View source for Custom Reports

== Custom Reports in GnuCash ==

The term ''Custom Reports'' has several contexts in GnuCash:
* Customizing settings for standard reports ([[Using GnuCash#Saved Report Configurations]])
* Combining selected standard reports into one view ([[Using GnuCash#Custom Multicolumn Report]])
* Customized output format for reports ([[Custom Reports Using Eguile]])
* Reports written in the Scheme programming language which are not delivered as part of the standard reports (this page)

If you are not up for coding, you should check the
* report options
* stylesheets and
* stylesheet options and
* file properties.
Possibly there are ways to get what you desire without coding.

If you are ready for coding (and even already firm in Scheme and Guile) then this is the place to contribute.

== Introduction ==

Unfortunately, at the present time writing a custom report for GnuCash requires a little bit of hacking. This wiki page should contain some information to help you get started, since there is no official documentation.

In the GnuCash project the reports are coded in ''Scheme'', not in ''C''. This is one of the pre-requisites to make the behaviour ready for customization.
It leads to the drawback that one must learn yet another programming language (if not already familiar with it) but saves the effort to get into the issue how to build GnuCash from source.

''Guile'' is used as interface to get the ''Scheme'' code executed during runtime. Again, if not already familiar with it, this is the second piece of work that one has to swallow.

Last but not least the API for that sort of thing is not formally specified.

Still reading? Not yet discouraged? Good on you! Because there is lots of help available.

First of all there is good educational stuff available on the web to get you into the topic of Scheme and Guile. Secondly there is a nice <code>hello-world.scm</code> example report specifically written to show you the base layout of a GnuCash report. And finally, this Wiki page might give you some guidence when doing the first steps.

== Getting Started ==

=== Get to know ''Scheme''===
GnuCash reports are written in the Scheme programming language. 

* Mastering Scheme is highly eased after reading [http://www.scheme.com/tspl4/ The Scheme Progamming Language] by R. Kent Dybvig

If you are new to ''Scheme'' it is not necessary to read and understand each bit of it right now. But you should at least have gone through the [http://www.scheme.com/tspl4/start.html#./start:h0 Getting Started] section.

=== Get to know ''Guile''===
Guile is used internally by GnuCash to interpret the Scheme reports. 

* [http://www.gnu.org/software/guile/docs/docs.html Guile documentation]

This comes with a marvellous [http://www.gnu.org/software/guile/docs/guile-tut/tutorial.html Tutorial]. You don't need this for writing the reports themselves, but it gives a clue of how reports are working in GnuCash and by that hopefully a good motivation to go and take the learning curve for ''Scheme''.

=== Get to know ''Gettext''===

That is the tool which makes the strings translatable. <code>(_ "Some Text")</code>, <code>(N_ "Some Text")</code> and similar mark the text for translation. See [[Translation#How to make strings in code translatable]] for details.

=== Where to find existing reports ===

The location of existing reports varies with by operating systems:

{| class="wikitable"
|-
!scope="col" style="width: 150px;" | Operating System
!scope="col"| GnuCash v2.6.x & v3.x
!scope="col"| GnuCash v2.4.x
|-
!scope="row"| BSD
| <tt>/usr/local/share/gnucash/scm/gnucash/report</tt>
| <tt>/usr/local/share/gnucash/guile-modules/gnucash/report</tt>
|-
!scope="row"| Debian including derivatives  such as Ubuntu
| <tt>/usr/share/gnucash/scm/gnucash/report</tt>
| <tt>/usr/share/gnucash/guile-modules/gnucash/report</tt>
|-
!scope="row"| Gentoo and Foresight
| <tt>/usr/share/gnucash/scm/gnucash/report</tt>
| <tt>/usr/share/gnucash/guile-modules/gnucash/report</tt>
|-
!scope="row"| OpenSuse 10.x and newer
| <tt>/usr/share/gnucash/scm/gnucash/report</tt>
| <tt>/usr/share/gnucash/guile-modules/gnucash/report</tt>
|-
!scope="row"| ''OpenSuse'' up to 10.x
| 
| <tt>/opt/gnome/share/gnucash/guile-modules/gnucash/report</tt>
|-
!scope="row"| ''OSX bundle'' (Gnucash.app)
| <tt>Gnucash.app/Contents/Resources/share/gnucash/scm/gnucash/report</tt>
| <tt>Gnucash.app/Contents/Resources/share/gnucash/guile-modules/gnucash/report</tt>
|-
!scope="row"| ''Windows''
| <tt><gnucash install dir*>\share\gnucash\scm\gnucash\report</tt>
| <tt><gnucash install dir*>\share\gnucash\guile-modules\gnucash\report</tt>
|}

(*) Note that on Windows, the installation directory is commonly "C:\Program Files\gnucash" on a 32-bit operating system (OS), and "C:\Program Files (x86)\gnucash" on a 64-bit OS.

=== Study some example reports ===

==== hello-world report ====
<tt>hello-world.scm</tt> was created to demonstrate the basic structure of a report. Don't get too confused by the huge number of options which are shown in this report - they were added to show off the variety of options available in GnuCash.

Have a look under [[#Where to find existing reports]] to find the source code for this report. Alternatively, you can browse [https://github.com/Gnucash/gnucash/blob/master/gnucash/report/utility-reports/hello-world.scm the current source code for this report on github].

By looking at the result of this report while you study the source code, you will easily get clues to how it functions. You can run this report in GnuCash via the menu:
* Reports
** Sample & Custom
*** Sample Report with Examples

==== account-piecharts report ====
If you want to walk through a much more complicated report, study [https://github.com/Gnucash/gnucash/blob/a39583c860bba3b3eb7ed399e47375e6ab6cf31f/src/report/standard-reports/account-piecharts.scm <tt>account-piecharts.scm</tt>].  

<span style="color:red">Warning</span>: this walkthrough is referring to a rather dated version of this report from 2011.  This walkthrough should probably be updated. The new path is https://github.com/Gnucash/gnucash/blob/master/gnucash/report/standard-reports/account-piecharts.scm.

There are two long functions in this report.
# [https://github.com/Gnucash/gnucash/blob/a39583c860bba3b3eb7ed399e47375e6ab6cf31f/src/report/standard-reports/account-piecharts.scm#L84 <code>option-generator</code>] defines the options for this report. 
# [https://github.com/Gnucash/gnucash/blob/a39583c860bba3b3eb7ed399e47375e6ab6cf31f/src/report/standard-reports/account-piecharts.scm#L191 <code>piechart-renderer</code>] makes all the calculations and renders the pie chart. 

The list of values to be shown in the pie chart is calculated by a [https://github.com/Gnucash/gnucash/blob/a39583c860bba3b3eb7ed399e47375e6ab6cf31f/src/report/standard-reports/account-piecharts.scm#L377  call to <code>traverse-accounts</code>] using the selected accounts stored in the <code>topl-accounts</code> variable. 

[https://github.com/Gnucash/gnucash/blob/a39583c860bba3b3eb7ed399e47375e6ab6cf31f/src/report/standard-reports/account-piecharts.scm#L336 <code>traverse-accounts</code>] is a recursive function that [https://github.com/Gnucash/gnucash/blob/a39583c860bba3b3eb7ed399e47375e6ab6cf31f/src/report/standard-reports/account-piecharts.scm#L349 calls itself] to traverse through all child accounts in the account tree. To get the balance for a single account, it makes a [https://github.com/Gnucash/gnucash/blob/a39583c860bba3b3eb7ed399e47375e6ab6cf31f/src/report/standard-reports/account-piecharts.scm#L346 <code>call to profit-fn</code>].  [https://github.com/Gnucash/gnucash/blob/a39583c860bba3b3eb7ed399e47375e6ab6cf31f/src/report/standard-reports/account-piecharts.scm#L253 <code>profit-fn</code>] obtains the account balance for either one interval or at a given date. It calls out to [https://github.com/Gnucash/gnucash/blob/a39583c860bba3b3eb7ed399e47375e6ab6cf31f/src/report/report-system/report-utilities.scm#L464 <code>gnc:account-get-comm-balance-at-date</code> in <code>src/reports/report-system/report-utilities.scm</code>] where, finally, lower level calls are made, which create a query for the account balance at the given date.

Well, long story short, this report is rather involved. Sorry.

=== Setup a prototype report ===

Even if you haven't ever written a report before, and you can't come up with a shiny track record of great ''Scheme'' experience, setting up a prototype at this moment will have the benefits getting productive after some time of pure theory.

The beginners amongst us might not have a final picture of what report to write. No worries, take the <tt>hello-world.scm</tt> report source file, store it in your preferred working directory, and rename it to a unique name, say <tt>my-world.scm</tt>.
As, for sure, you already have read through this report, you know that this report is very wordy, giving a lot of text printouts. These can be used to easily see your own first changes on the screen once this prototype is loaded into GnuCash, and even better, it will let you differentiate between the <tt>my-world.scm</tt> that you have loaded and the <tt>hello-world.scm</tt> that is available in GnuCash by default (see previous section). So feel free to implement some fancy printout changes.

==== Prerequisites ====

''GnuCash'' will not be able to load your report until you make changes in two areas of your report source file:

===== Give report a unique symbol name =====
To avoid symbol definition conflicts with other reports, make sure your report code begins with a '''define-module statement''' with a report name not used by any other report, for example:
 (define-module (gnucash report <span style="color:green">my-world-report</span>))

===== Define report with unique name and id =====   
To enable ''GnuCash'' to register your report into the Report menu, scroll to the end of the code and update the '''gnc:define-report statement'''.

Set the '''name''' of your report to be shown in the  Report menu. For GnuCash 2.2.x and before this name must be unique across all reports.
 'name (N_ "<span style="color:green">My World</span>")

Further down below, if it is present, comment out the '''menu-name''' line: 
<pre>;;'menu-name (N_ "Sample Report with Examples")</pre>

Update the '''tool tip''' text to something appropriate for your report:
 'menu-tip (N_ "<span style="color:green">Unstable. Used for Testing.</span>")

For GnuCash 2.3.x and later, your report must have a globally unique identifier (guid). GnuCash will fail to start if multiple reports have the same unique id. For this reason, if you wish to create a backup of a report while you work on it, place the backup outside the GnuCash directories. If you need some newly generated unique id, run the program:
 uuidgen | sed -e 's/-//g'
or use an online uuid generator like [https://www.guidgenerator.com/ this one] (any other one will do as well). Be sure to untick "Hyphens" to generate gnucash compatible guids. If you forget or the site you use doesn't offer that option, simply remove the hyphens yourself.
Copy the newly generated ID and paste it into the '''report-guid''' value:
 'report-guid "<span style="color:red">paste generated report unique id here</span>"

=== Loading Your Report ===
There are ''two ways to load a report'' at startup of GnuCash:
* from a user account or
* from the installation tree.
You will likely want to use the user account approach - a least until your work is finished.

==== Load the report from a user account ====

This method is used if you edit your report source file in a working directory.

A) Go to your settings directory:

{| class="wikitable"
|-
!scope="col"| Operating System
!scope="col"| Settings Directory (2.6 and older)
!scope="col"| Settings Directory (3 and newer)
|-
!scope="row"| ''Linux/Unix''
| <tt>/home/YourName/.gnucash</tt>
| <tt>/home/YourName/.config/gnucash</tt>
|-
!scope="row"| ''Windows 7 and newer''
| <tt>C:\Users\YourName\.gnucash</tt>
| <tt>C:\Users\YourName\AppData\Roaming\GnuCash</tt>
|-
!scope="row"| ''Windows XP & Vista''
| <tt>C:\Documents and Settings\YourName\.gnucash</tt>
| (Not supported)
|-
!scope="row"| ''OSX Bundle'' (Gnucash.app) 
| Under your home directory: <tt>Library/Application Support/Gnucash</tt> 
(if you are still using macOS 10.6 or earlier: <tt>Library/Applications Defaults/Gnucash</tt>)
| Under your home directory: <tt>Library/Application Support/Gnucash</tt> 
|}

B) Edit the respective user config file to load your custom report.

* For GnuCash v2.x edit <tt>config.user</tt> to add a line of the form:

<SyntaxHighlight lang="scheme">
(load (gnc-build-dotgnucash-path "my-report.scm"))
</SyntaxHighlight>

* For GnuCash v3.x edit <tt>config-user.scm</tt> to add a line of the form:

<SyntaxHighlight lang="scheme">
(load (gnc-build-userdata-path "my-report.scm"))
</SyntaxHighlight>

'''Note:''' ''(gnc-build-dotgnucash-path ...)'' or ''(gnc-build-userdata-path ...)'' respectively will complement your report name with the full path of your settings directory as shown in above table.

* If the <tt>config.user</tt> or <tt>config-user.scm</tt> file is not yet found in your settings directory, simply create it.

Move, copy, or link* your report file (<tt>my-report.scm</tt>) from your working directory to the above settings directory. The report should be visible in the Reports menu after the next restart.

<tt>*</tt> On Unix-like OSs you can use the <tt>ln</tt> command; on Windows (7 and higher) you can use the <tt>mklink</tt> command.

'''Caution:''' For older versions of GnuCash (before 2.1.x ?) ''load-from-path'' was suggested to load reports instead of ''load'', but this is not compatible with the module definition that is now found in all reports. Using ''load-from-path'' on a report with module defninition will cause [https://bugzilla.gnome.org/show_bug.cgi?id=618670 a crash]

To reload your report, you must '''restart''' GnuCash. You will have to do this '''every time''' you change a report.

''Thanks to [[User:DeanCording|DeanCording]] for clarifying the define-module/load bits''

==== Load the report from the installed report directory ====
While not recommended you can also copy the report to the installed report directory.  Make sure you have included a module definition as shown above.  All *.scm files from the directory guile-modules/gnucash/report/standard-reports/ will be loaded automatically. This applies ''only'' to the standard-reports/ sub-directory, not to any of the other directories with reports. Hence, the easiest way to have your report available to gnucash is to copy your *.scm file into that directory.

Then '''restart''' GnuCash. You will have to do this '''every time''' you change the report definition file.

=== Debugging your report ===
When guile cannot make sense of your report, or your report throws an error, GnuCash will present the following error message in place of your report:
{| class="wikitable"
|-
|'''Report error'''
An error occurred while running the report.
|}

This lets you know there was a problem, but now you need to pinpoint where the problem lies.  Here are some tips that might help.

{| class="wikitable"
|- 
! scope = "col" | Tip
! scope = "col" | Details

|- style="vertical-align:top;"
| Enable debug messages
| Start GnuCash with debug command line parameters: <syntaxhighlight lang="sh">gnucash --debug --log gnc.scm=debug</syntaxhighlight>  
On MacOS, assuming GnuCash is in your <code>/Applications</code> folder, this would be:
<syntaxhighlight lang="sh>/Applications/Gnucash.app/Contents/MacOS/Gnucash --debug --log gnc.scm=debug</syntaxhighlight>
There are other debug related options, run GnuCash with the <code>--help</code> for a complete list.
|- style="vertical-align:top;"
| Study the trace logs
| The GnuCash trace logs can sometimes give you that satisfying "oh, I see". By default you'll find the trace log:
{| class="wikitable"
|- 
! scope ="col" | Operating System
! scope ="col" | Location
|- style="vertical-align:top;"
| Unix/Linux
| <code>$TEMP/gnucash.something.trace</code>
|- style="vertical-align:top;"
| Windows
| <code>%TEMP%/gnucash.something.trace</code>
|- style="vertical-align:top;"
| MacOs
| Somewhere under <code>/var/folders/</code> You can find it via:
<syntaxhighlight lang="sh">find /var/folders -name "gnucash.trace" 2> /dev/null</syntaxhighlight>
|}
You can change the trace log file location via GnuCash command line parameter <code>--logto</code>. This parameter includes support for logging to <code>'stderr'</code> and <code>'stdout'</code>

|- style="vertical-align:top;"
| Add your own debug messages
| You can use the <code>gnc:debug</code> function to add your own messages.  For example: <syntaxhighlight lang="scheme">(gnc:debug "here I am")</syntaxhighlight>

|- style="vertical-align:top;"
| Add other messages
| There are also <code>gnc:msg</code>, <code>gnc:warn</code> and <code>gnc:error</code> functions; see [https://github.com/Gnucash/gnucash/blob/unstable/libgnucash/scm/utilities.scm] for more details.

|- style="vertical-align:top;"
| Use a Scheme friendly editor
| For the uninitiated, matching parentheses properly in a Scheme program can make one's eyes cross. A Lisp/Scheme friendly editor can really help here. DrRacket or a properly configured Emacs really helps.

|- style="vertical-align:top;"
| Run often
| Test your report often after making very small changes.  This will make it easier to understand when and where problems are introduced.
|}

Although guile does have debug support, this wiki page updater has not found a way, at this time, to hook GnuCash up to the guile debugger.

== Development Environment ==

=== Programming tools ===

Any reasonable source/text editor, including emacs and vi, should provide basic syntax support for source-code editing.  One of the most basic and important for editings scheme/lisp sources is parenthesis matching.  Other scheme-like environments (such as [http://racket-lang.org/ DrRacket]) might also be useful for editing the sources, but note that they might allow constructs that are not valid in guile. Beware Racket is a scheme dialect not 100% compatible with Guile, but provides a nice GUI for understanding scheme functions.

=== Simple Proposal for Linux ===

This is a simple proposal for a development environment in Linux.
Assume 
* there is a working directory <code>~/GnuCash/CustomReports</code> in your home directory.
* the new report is stored in the <code>test00.scm</code> file
Here is the proposal how to setup up your environment
<syntaxhighlight lang="sh">
cd ~/GnuCash/CustomReports
ln -s test00.scm prototype.scm
cat > config.user << "EOF"
(load "<fullPathTo>/GnuCash/CustomReports/prototype.scm")
EOF
cd ~/.gnucash
ln -s ~/GnuCash/CustomReports/config.user
uuidgen | sed -e s/-//g
</syntaxhighlight>

Prepare <code>test00.scm</code> to include
* the define-module statement 
<syntaxhighlight lang="scheme">(define-module (gnucash report prototype-report))</syntaxhighlight>
* following updates in the <code>gnc:define-report</code> statement
<syntaxhighlight lang="Scheme">'name (N_ "Prototype")
;;'menu-name (N_ "Sample Report with Examples")
'menu-tip (N_ "Unstable. Used for Testing.")
'report-guid "the-new-generated-unique-ID"</syntaxhighlight>

See also the minimum report defintion in the [[#Designing new Reports]] chapter.

By this you can
* use <code>test00.scm</code> as a template test report and use the lines as described above without further changes
* collect all our test reports as e.g. testXX.scm files in this directory
* switch between them by making the prototype.scm point to the desired report
* restart GnuCash
* always find the report under ''Reports->Sample & Custom Report->Prototype''

Finally, you should also extract a ''GnuCash'' source tar ball in <code>~/GnuCash/CustomReport/</code> to have access to the ''Scheme'' files referenced in this page.

=== Technique to reload reports without restarting GnuCash ===

Reports can be modified to allow the majority of the report to be
reloaded without requiring GnuCash to be restarted for each change
which is very convenient when developing reports.  This requires splitting
the report into two files:

# a minimal loader which which forces the reload of the meat of your report each time options are generated or report is rendered.
# the meat of your report.  This contains actual report code for the options generator and renderer.

Both files must parse and execute correctly before the reload will function. 

Note that, at least in GnuCash 2.6.17, for changes to report options to take effect,  the report must closed and then relaunched from the Report menu. Changes to the render portion seem to be handled just fine by the reload button. 

====Minimal Example ====
The following is a skeleton outline of what is required for a report 
to be reloaded on the fly. Tested with GnuCash 2.6.17.

=====Minimal Loader  =====
Update <code>name</code>, <code>report-guid</code> and <code>menu-tip</code> values appropriately for your report.

custom_import.scm:
<syntaxhighlight lang="scheme" highlight="24-26">
(define-module (custom_import))
(use-modules (gnucash gnc-module))
(use-modules (gnucash gettext))
(gnc:module-load "gnucash/report/report-system" 0)
; load the renderer module once at the top level to get the symbols
(use-modules (custom_import_renderer))

; get and reload the module
(define (reload-report-module)
  (reload-module (resolve-module '(custom_import_renderer))))

; every time options are generated, reload the meat of the report
(define (options_loader)
  (reload-report-module)
  (custom_import_options))

; every time report is rendered, reload the meat of the report
(define (renderer_loader report-obj)
  (reload-report-module)
  (custom_import_renderer report-obj))
 
(gnc:define-report
 'version 1
 'name (N_ "<type your report name here>")
 'report-guid "<paste report unique id here>"
 'menu-tip (N_"<type your report menu tip here>")
 'menu-path (list gnc:menuname-utility)
 'options-generator options_loader
 'renderer renderer_loader)
</syntaxhighlight>

=====The Meat of Your Report =====
custom_import_renderer.scm:
<syntaxhighlight lang="scheme">
(define-module (custom_import_renderer))
 
; options for the report (called by loader after it reloads this module)
(define (custom_import_options)    
  (let* ((options (gnc:new-options)))  
    ; add your options here       
    options))
 
; report renderer (called by loader after it reloads this module)
(define (custom_import_renderer report-obj) 
  (let ((document (gnc:make-html-document)))
      ; add your renderer here
      document))

(export custom_import_options)
(export custom_import_renderer)
</syntaxhighlight>

=====Configuration =====
You'll also need to edit config.user so that GnuCash can find the files above.
Update <code>add-to-load-path</code> value appropriately for your setup.

config.user:
<syntaxhighlight lang="scheme" highlight="1">
(add-to-load-path "<type the full path to above report files here>")
(use-modules (custom_import))
</syntaxhighlight>

== Designing new Reports ==

In general, reports are divided into three sections
* the Options-Generator (define the options for the report)
* the Report-Renderer (create the HTML report)
* the <code>gnc:define-report</code> statement (makes the report available in ''GnuCash'')

This is the minimum definition needed for a new ''GnuCash'' report. Update <code>name</code>, <code>report-guid</code> and <code>menu-tip</code> values appropriately.

<syntaxhighlight lang="scheme" highlight="40-42">
;; -*-scheme-*-

;; This is a minimum report definition in GnuCash.
;; It illustrates the the minimum definitions needed to create
;; a new GnuCash report.
;; It will create an empty page with heading 'Prototype'.
;; To be used as template.

;; ------------------------------------------------------------------
;; Top-level definitions
;; ------------------------------------------------------------------

(define-module (gnucash report prototype))
(use-modules (gnucash gnc-module))
(use-modules (gnucash gettext))
(gnc:module-load "gnucash/report/report-system" 0)

;; ------------------------------------------------------------------
;; Define the Options for this report
;; ------------------------------------------------------------------

(define (options-generator)    
  (let* ((options (gnc:new-options)))         
    options))

;; ------------------------------------------------------------------
;; Render the HTML document
;; ------------------------------------------------------------------

(define (document-renderer report-obj)
  (let ((document (gnc:make-html-document)))
      document))

;; ------------------------------------------------------------------
;; Define the actual report
;; ------------------------------------------------------------------

(gnc:define-report
 'version 1
 'name (N_ "Prototype")
 'report-guid "<paste generated unique report id here>"
 'menu-tip (N_ "Unstable. Used for Testing.")
 'menu-path (list gnc:menuname-utility)
 'options-generator options-generator
 'renderer document-renderer)
</syntaxhighlight>

=== The Options-Generator ===

Each report takes responsibility to build up an own database that holds the options for the report.

Usually it is a good habit to copy the relavant code from the <code>hello-world.scm</code>.
In there you will find the database initializing 
*call to <code>gnc:new-options</code> 
which will 
*create the container called <code>options</code>
which will later on be filled by 
*calling the help function <code>add-option</code>
which is a nice wrapper to eventually
*call <code>gnc:register-option</code>

The <code>gnc:...</code>-procedures to create this database and to fill it with values are contained in <code>gnucash/src/app-utils/options.scm</code>.

<code>gnucash/src/report/utility-reports/hello-world.scm</code> presents a nice selection of example option definitions of following types:
<syntaxhighlight lang="scheme">
gnc:make-simple-boolean-option
gnc:make-multichoice-option
gnc:make-string-option
gnc:make-date-option
gnc:make-number-range-option
gnc:make-color-option
gnc:make-account-list-option
gnc:make-list-option
</syntaxhighlight>

On top of these, you find
<syntaxhighlight lang="scheme">
gnc:make-text-option
gnc:make-font-option
gnc:make-currency-option
gnc:make-budget-option
gnc:make-commodity-option
gnc:make-complex-boolean-option
gnc:make-pixmap-option 
gnc:make-account-list-limited-option
gnc:make-account-sel-option
gnc:make-account-sel-limited-option
gnc:make-multichoice-callback-option
gnc:make-radiobutton-option
gnc:make-radiobutton-callback-option
gnc:make-internal-option
gnc:make-query-option
gnc:make-dateformat-option
</syntaxhighlight>
in <code>gnucash/src/app-utils/options.scm</code>.

Also, <code>gnucash/src/business/business-utils/business-options.scm</code> provides some options
<syntaxhighlight lang="scheme">
gnc:make-invoice-option
gnc:make-customer-option
gnc:make-vendor-option
gnc:make-employee-option
gnc:make-owner-option
gnc:make-taxtable-option
gnc:make-counter-option
gnc:make-counter-format-option
</syntaxhighlight>

In general, the syntax for creating an option is:
<syntaxhighlight lang="scheme">
(define (gnc:make-<type>-option
         section                      ;; the tab-string in the option dialog presented to the user
         name                         ;; the text for this option in the option dialog presented to the user
         sort-tag                     ;; used to define the order in which the options are listed
         documentation-string         ;; help string shown when the mouse moved over the option
         default-value
         <optional type specific parameters>)
</syntaxhighlight>

Note that <code>section</code> is free to be any text string. If section-string has not been used before, a new tab with this name will be created automatically. Nevertheless, note that <code>gnucash/src/report/report-system/report.scm</code> provides three default names. Re-use these before creating new names:
<syntaxhighlight lang="scheme">
(define gnc:pagename-general (N_ "General"))
(define gnc:pagename-accounts (N_ "Accounts"))
(define gnc:pagename-display (N_ "Display"))
</syntaxhighlight>

For a start, simply read through the <code>define (options-generator)</code> statement in <code>hello-world.scm</code> and copy what you need.

Nice to know:

* The ''General'' option group does not need to be defined, it is part of the report definition per default. If you run the above minimum report definition, the ''General'' option group will automatically include a text field for the <code>Report Name</code>, a selection box for the <code>Stylesheet</code>, and a button to <code>Reset defaults</code>.
* To find the option creation procedures in the source file tree you can use <syntaxhighlight lang="sh">grep gnc:make-.*-option `find . -name "*.scm"` | grep define</syntaxhighlight>
* The source file tree is found in
** Debian and Ubuntu Linux: <code>/usr/share/gnucash/scm</code>

=== The Report-Renderer ===

Define how to apply the options (the actual report contents).

The overall goal of the ''Report-Renderer'' is to create an ''HTML''-document and fill it in with the reports results to display it out to the user.

Similar as with the ''Options-Generator'', <code>hello-world.scm</code> gives you a great introduction how this works in general.

The <code>gnc:...</code>-procedures are found in the <code>src/report/report-system/html-*.scm</code> source files.

After runnning the report you can press the <code>Export</code> button to save the generated ''HTML-Code'' into a file for viewing. Doing this for the above minimum prototype report gives the following result:
<syntaxhighlight lang="html">
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<style type="text/css">
h3 { font-family: Ubuntu; font-size: 15pt; font-weight: bold;  }
a { font-family: Ubuntu; font-size: 10pt; font-style: italic;  }
body, p, table, tr, td { text-align: left; font-family: Ubuntu; font-size: 10pt;  }
tr.alternate-row { background: #ffffff }
th.column-heading-left { text-align: left; font-family: Ubuntu; font-size: 10pt;  }
th.column-heading-center { text-align: center; font-family: Ubuntu; font-size: 10pt;  }
th.column-heading-right { text-align: right; font-family: Ubuntu; font-size: 10pt;  }
td.neg { color: red;  }
td.number-cell, td.total-number-cell { text-align: right; white-space: nowrap; }
td.date-cell { white-space: nowrap; }
td.anchor-cell { white-space: nowrap; font-family: Ubuntu; font-size: 10pt;  }
td.number-cell { font-family: Ubuntu; font-size: 10pt;  }
td.number-header { text-align: right; font-family: Ubuntu; font-size: 10pt;  }
td.text-cell { font-family: Ubuntu; font-size: 10pt;  }
td.total-number-cell { font-family: Ubuntu; font-size: 12pt; font-weight: bold;  }
td.total-label-cell { font-family: Ubuntu; font-size: 12pt; font-weight: bold;  }
td.centered-label-cell { text-align: center; font-family: Ubuntu; font-size: 12pt; font-weight: bold;  }
</style>
<title></title>
</head>

<body bgcolor="#ffffff">
<h3></h3>
</body>
</html>
</syntaxhighlight>
The style section is added automatically without specific definitions inside the prototoype source.
Also note that the register name in ''GnuCash'' is not part of the ''HTML'' document.

The procedures to fill this ''HTML''-document with life and further formatting are given in source tree below
* Linux Ubuntu: <code>/usr/share/gnucash/scm</code> 
in the following files:
<pre>
html-acct-table.scm
html-barchart.scm
html-document.scm
html-fonts.scm
html-linechart.scm
html-piechart.scm
html-scatter.scm
html-style-info.scm
html-style-sheet.scm
html-table.scm
html-text.scm
html-utilities.scm
</pre>

Start making the prototype report a little nicer by adding the following line to the <code>document-renderer</code> from <code>html-document.scm</code>
<syntaxhighlight lang="scheme">
(gnc:html-document-set-title! document (_ "GnuCash Report Prototype"))
</syntaxhighlight>
will result in an update of the <code>title</code> and <code>h3</code> lines:
<syntaxhighlight lang="html">
[...]
<title>GnuCash Report Prototype</title>
[...]
<h3>GnuCash Report Prototype</h3>
[...]
</syntaxhighlight>

Next it is possible to add attributes to the body line.

'''''Note:''''' 
You should read the following section for informational purposes only: Style sheets are now the preferred way to specify a document's presentation, the presentational attributes of BODY have been deprecated. ([http://www.w3.org/TR/html401/struct/global.html#edef-BODY quoted from W3.org])
(Currently in ''GnuCash'' the <code>bgcolor</code>-tag is default part of the <code>body</code>-tag.)

The <code>body</code>-tag can be enhanced with attributes via the <code>gnc:html-document-set-style!</code> funtion. The general sytax:
<syntaxhighlight lang="scheme">
(gnc:html-document-set-style!
    document                               ;; the reference to the current html-document
    "body"                                 ;; specify the tag to add attributes to
    'attribute (list "blabla" "balabala")  ;; first additional attribute
    'attribute (list "nonstop" "nonsens")  ;; second additional attribute
    'attribute (list "bgcolor" "#f6ffdb")  ;; third additional attribute
    [...]                                  ;; further attributes
)
</syntaxhighlight>

The example above lists some imaginary attributes to indicate that the attribute definition will be added to the <code>body</code>-tag without further validity check. Invalid attributes will appear in the ''HTML''-code but will have no visible effect on the document representation.

The rest of the body is filled with ''HTML''-text by defintion of text objects, which gives the following structure
<syntaxhighlight lang="html">
<body bgcolor="#ffffff">
<h3>[title]</h3>

  [text object 1]
  [text object 2]
    .     .    .
    .     .    .
    .     .    .
  [text object n]

</body>
</syntaxhighlight>
whereas it does not matter if you define one or more text objects, you can put everything into one object or split it over several objects.

In ''Scheme'' these objects are defined like
<syntaxhighlight lang="scheme">
(gnc:html-document-add-object!
    document               ;; the overall HTML document defined above
    (gnc:make-html-text    ;; a text object
        [text 1]             ;; part 1 of the text
        [text 2]             ;; part 2 of the text
             .   .
             .   .
             .   .
        [text m]             ;; part m of the text
    )
)
</syntaxhighlight>
Note the above structure is the definition of 1 text object, which consists of m (sub-)text elements.

The text elements can be simple strings, or ''markup''-formatted. ''Markup''-commands are found in
* Linux Ubuntu: <code>/usr/share/gnucash/scm/html-text.scm</code>:

<syntaxhighlight lang="scheme">
gnc:html-markup-p        ;; markup for "paragraph"
gnc:html-markup-tt       ;; markup for fixed font (type writer style)
gnc:html-markup-em       ;; markup for "emphasis"
gnc:html-markup-b        ;; markup for "bold"
gnc:html-markup-i        ;; markup for "italic"
gnc:html-markup-h1       ;; markup for headers on level 1
gnc:html-markup-h2       ;; markup for headers on level 2
gnc:html-markup-h3       ;; markup for headers on level 3
gnc:html-markup-br       ;; markup for line "break" (no text)
gnc:html-markup-hr       ;; markup for "horizontal line" (no text)
gnc:html-markup-ul       ;; markup for "unsorted list" (bullet list)
gnc:html-markup-anchor   ;; markup for hyperlinks
gnc:html-markup-img      ;; markup for images
</syntaxhighlight>

To give you a basic idea, an example of simple text objects:
<syntaxhighlight lang="scheme">
(gnc:html-document-add-object!
     document
     (gnc:make-html-text 
        "some text" 
        "some other text" 
        (gnc:html-markup-br)
        (gnc:html-markup-tt "tt text")
        (gnc:html-markup-h1 "header1 text")
        (gnc:html-markup "bla" "tirili flöt")
        (gnc:html-markup "i" "italic text")
    )
)
</syntaxhighlight> 

results in following ''HTML''-code
<syntaxhighlight lang="html">
<body bgcolor="#f6ffdb">
<h3>GnuCash Report Prototype</h3>
some text some other text
<br />
<tt>tt text</tt>
<h1>header1 text</h1>
<bla>tirili flöt</bla>
<i>italic text</i>
</body>
</syntaxhighlight>
Note that it is possible to define new tags (here: "bla") if needed by using <code>gnc:html-markup</code>.

Again: Take a good look at <code>hello-world.scm</code> and explore many more examples how to format ''HTML''-text.
 
Examine:
<pre>
html-scatter.scm
html-acct-table.scm
html-piechart.scm
html-table.scm
html-linechart.scm
</pre>
to find out more about
<syntaxhighlight lang="scheme">
gnc:make-html-scatter
gnc:make-html-acct-table
gnc:make-html-barchart
gnc:make-html-table
gnc:make-html-linechart
</syntaxhighlight>

=== The <code>gnc:define-report</code> Statement ===

If you want to follow the [[#Simple Proposal for Linux]] to setup a simple development environment then you need updates to this section only
* once that you set up the development environment
* once that your report is ready, fully tested, and shall become part of your standard reports

And again, <code>hello-world.scm</code> already proposes how you should proceed in the latter case
<pre>
[...] 
to contribute your brand new, totally cool report, consult the mailing list "mailto:gnucash-devel@gnucash.org"
[...]
</pre>

=== Barcharts ===

The minimum definition is of a bar chart report is shown in the following example.  Before running, update <code>name</code>, <code>report-guid</code> and <code>menu-tip</code> values appropriately.

<syntaxhighlight lang="scheme" highlight="60-62">
;; -*-scheme-*-

;; This is a minimum barchart report definition in GnuCash.
;; It illustrates the the minimum definitions needed to create
;; a new GnuCash barchart report.
;; It will create a page with heading 'Prototype'.
;; To be used as template.

;; ------------------------------------------------------------------
;; Top-level definitions
;; ------------------------------------------------------------------

(define-module (gnucash report prototype))
(use-modules (gnucash gnc-module))
(gnc:module-load "gnucash/report/report-system" 0)

;; ------------------------------------------------------------------
;; Define the Options for this report
;; ------------------------------------------------------------------

(define (options-generator)    
  (let* ((options (gnc:new-options)))         
    options))

;; ------------------------------------------------------------------
;; Render the HTML document
;; ------------------------------------------------------------------

(define (document-renderer report-obj)
  (let (
         (document (gnc:make-html-document))
         (chart (gnc:make-html-barchart))
       )

       (gnc:html-barchart-set-title! chart "Barchart Title")		;; optional
       (gnc:html-barchart-set-subtitle! chart "Barchart Sub-Title")	;; optional
       (gnc:html-barchart-set-width! chart 400)
       (gnc:html-barchart-set-height! chart 400)
       (gnc:html-barchart-set-row-labels! chart '("row1" "row2"))
       (gnc:html-barchart-set-y-axis-label! chart "y-Axis-Label")	;; optional
       (gnc:html-barchart-set-x-axis-label! chart "x-Axis-Label")	;; optional
       (gnc:html-barchart-append-column! chart '(100 200))
       (gnc:html-barchart-append-column! chart '(110 210))

       (gnc:html-barchart-set-col-labels! chart '("col1" "col2"))
       (gnc:html-barchart-set-col-colors! chart '("green" "blue"))
       
       (gnc:html-document-add-object! document chart)

       document ;; RETURN value
  )
)

;; ------------------------------------------------------------------
;; Define the actual report
;; ------------------------------------------------------------------

(gnc:define-report
 'version 1
 'name (N_ "Prototype")
 'report-guid "<paste generated unique report id here>"
 'menu-tip (N_ "Unstable. Used for Testing.")
 'menu-path (list gnc:menuname-utility)
 'options-generator options-generator
 'renderer document-renderer)
</syntaxhighlight>

If you look at the HMTL source for this report after it is generated, you will see a line  with the <code><img></code> tag. The image for the report is encoded inline in a very long ASCII code string.

<syntaxhighlight lang="html">
<img src="data:image/png;base64,<very_long_ASCII_coded_string>" alt="Cannot display barchart"/> &nbsp;
</syntaxhighlight>

== The GnuCash API ==
The GnuCash application programming interface ([http://code.gnucash.org/docs/MAINT/ maint] or [http://code.gnucash.org/docs/MASTER/ master] branch) is quite intimidating, unfortunately. Luckily, for the reports, most of the stuff needed can be found in the scheme sources. Here some random examples of handy procedures  (paths shown refer to the location in a source tarball; might be copied into the location as above in your installation):
* create a monetary object via <code>gnc:make-gnc-monetary</code> <tt>src/engine/gnc-numeric.scm</tt>
* get the amount of a monetary object via <code>gnc:gnc-monetary-amount</code> <tt>src/engine/gnc-numeric.scm</tt>
* get an account name via <code>gnc-account-get-name</code> <tt>src/engine/swig-engine.c</tt>
* create a commodity collector via <code>gnc:make-commodity-collector</code> <tt>src/report/report-system/report-utilities.scm</tt>

The mightiness of the API is huge. As of GnuCash 2.4.10, there were over 1000 GnuCash api calls that could be made from reports.

It is by far too much to be documented in this Wiki-page.

However, having a table at hand which includes the most common function calls is convenient especially at the start of digging into it.

That is why following table is included in this chapter. The table does not purport to be exhaustive, nor even aim to be, but ''Scheme''-Report developers are invited to add to this table whenever they come across additions of general interest.

{| class="wikitable"
|-
! scope="col"| Name
! scope="col"| Source
! scope="col"| Example
! scope="col"| Comments

|- style="vertical-align:top;"
| style="white-space: nowrap;" | gnc:account-get-balance-at-date
| style="white-space: nowrap;" | report-utilities.scm
| 
| Returns the account balance as a gnc-numeric record. 
(NEW) You can convert to scheme rational by using <tt>gnc-numeric-to-scm</tt> Example:
<syntaxhighlight lang="scheme">
(gnc-numeric-to-scm (gnc:account-get-balance-at-date acct date #f))
</syntaxhighlight>

(OLD) To get the float value, you can use <tt>gnc:gnc-numeric-num</tt> and <tt>gnc:gnc-numeric-denom</tt> (see below). Example:
<syntaxhighlight lang="scheme">
(let* (
        (bal 
            (gnc:account-get-balance-at-date
               acct 
               date
               #f ;; include children?
            )
        )
        (num (gnc:gnc-numeric-num bal))
        (denom (gnc:gnc-numeric-denom bal))
      )
      (/ num denom 1.0)
)
</syntaxhighlight>

|- style="vertical-align:top;"
| gnc:html-table-append-row!
| html-table.scm
|
| Appends a row to an HTML table. 
Note that <tt>row</tt> can be a list. If so, then each list element represents a column entry.
Example:
<syntaxhighlight lang="scheme">(gnc:html-table-append-row! table (list e1 e2 e3))</syntaxhighlight>
will result in:
<syntaxhighlight lang="html">
<tr>
<td>e1<td>
<td>e2<td>
<td>e3<td>
</tr>
</syntaxhighlight>
Note that only simple lists are supported for. If you use nested lists as input, then the whole list contents of the nested lists will be displayed.

|- style="vertical-align:top;"
| gnc:gnc-numeric-denom
| gnc-numeric.scm
|
| Returns the denominator part of a gnc-numeric record.

|- style="vertical-align:top;"
| gnc:gnc-numeric-num
| gnc-numeric.scm
|
| Returns the numerator part of a gnc-numeric record.

|- style="vertical-align:top;"
| gnc-account-get-full-name
| gnc_account_get_full_name() in Account.c
| hello-world.scm
| Returns the account name in the format
<tt>ParentLevel1:ParentLevel2:...:AccountName</tt>

To only get the <tt>AccountName</tt> use <tt>xaccAccountGetName</tt>

|- style="vertical-align:top;"
| gnc-transaction-get-date-posted
| gnc_transaction_get_date_posted() in engine-helpers.c
|
| Returns the posting date of a transaction. Transactions are return e.g. by <tt>xaccSplitGetParent</tt>, see below. Note that this function will return the date as numerical value. If you need to have it human readable, you need to convert this numerical value into a date string, like so:
<syntaxhighlight lang="scheme">
(gnc-print-date (gnc-transaction-get-date-posted (xaccSplitGetParent split)))
</syntaxhighlight>

|- style="vertical-align:top;"
| gnc-window-show-progress
| gnc_window_show_progress() in gnc-window.c
| report-utilities.scm
| Used to forward processing progress information to the user. In <tt>report-utilities.scm</tt> this is wrapped in the routines:
* <tt>gnc:report-starting
* gnc:report-render-starting
* gnc:report-percent-done
* gnc:report-finished</tt>
The standard report <tt>cash-flow.scm</tt> makes use of this api.

|- style="vertical-align:top;"
| xaccAccountGetDescription
| Account.c
|
| Returns the account description. To be used with the account as input parameter:
<syntaxhighlight lang="scheme">(xaccAccountGetDescription acct)</syntaxhighlight>

|- style="vertical-align:top;"
| xaccAccountGetName
| Account.c
| hello-world.scm
| Returns the account name. To get the full account name including parent names use <tt>gnc-account-get-full-name</tt> 

|- style="vertical-align:top;"
| xaccAccountGetNotes
| Account.c
|
| Returns the account notes. This is the text field that is found in the <tt>edit</tt> dialog of the accounts. To be used with the account as input parameter: 
<syntaxhighlight lang="scheme">(xaccAccountGetNotes acct)</syntaxhighlight>

|- style="vertical-align:top;"
| xaccAccountGetSplitList
| Account.c
| report-utilities.scm
| Returns the the list of transactions in a given account. Note that in ''GnuCash'' each transaction is a split even if it is not a split transaction. A non-split transaction is a transaction consisting of a single split.
To get the numerical value for the amount of splits in a list of accounts use <tt>gnc:accounts-count-splits</tt> defined in <tt>report-utilities.scm</tt>.
The standard report <tt>cash-flow.scm</tt> makes use of this api.

|- style="vertical-align:top;"
| xaccAccountGetType
| Account.c
|
| Returns the account type, which is the text field that is found in the <tt>edit</tt> dialog of the accounts. To be used with the account as input parameter <tt>(xaccAccountGetNotes acct)</tt>
The following account types are available: 
<tt>
* ACCT-TYPE-BANK
* ACCT-TYPE-CASH
* ACCT-TYPE-CREDIT
* ACCT-TYPE-ASSET
* ACCT-TYPE-LIABILITY
* ACCT-TYPE-STOCK
* ACCT-TYPE-MUTUAL
* ACCT-TYPE-CURRENCY
* ACCT-TYPE-INCOME
* ACCT-TYPE-EXPENSE
* ACCT-TYPE-EQUITY
* ACCT-TYPE-CHECKING
* ACCT-TYPE-SAVINGS
* ACCT-TYPE-MONEYMRKT
* ACCT-TYPE-RECEIVABLE
* ACCT-TYPE-PAYABLE
* ACCT-TYPE-CREDITLINE
* ACCT-TYPE-TRADING</tt>

|- style="vertical-align:top;"
| xaccSplitGetAccount
| Split.c
|
| Returns the account object that the split belongs to. To get the name from the returned account, use:
<syntaxhighlight lang="scheme">(xaccAccountGetName (xaccSplitGetAccount split))</syntaxhighlight>

|- style="vertical-align:top;"
| xaccSplitGetCorrAccountName
| Split.c
|
| Returns the account name at the other end of the split as a string.

|- style="vertical-align:top;"
| xaccSplitGetParent
| Split.c
|
| Returns the parent transaction the split belongs to. See <tt>gnc-transaction-get-date-posted</tt> for an example how to use it.

|}


=== Command line access to the API ===

(Written Jan 2018)
It is convenient to access the full API from a Guile Command-line for newbie report developers. This requires the developer is familiar with Linux, and can set up CMake, unit testing environments.

The full GUI-generated reporting construct described above is important to test a custom report, however, is very inconvenient to explore the API.

The preparation work involves:

1. Create a special unit test program in scheme, perhaps naming it test-server.scm - this shall reside in a convenient folder with other unit test files e.g. gnucash/report/standard-reports/test.

<syntaxhighlight lang="scheme">
(use-modules (gnucash gnc-module))
(gnc:module-begin-syntax (gnc:module-load "gnucash/app-utils" 0))
(use-modules (gnucash engine test test-extras))

;; The following needed for Guile REPL
(use-modules (system repl server))
(define (run-test)
  (run-server))

;; The following needed for reports:
(use-modules (gnucash report stylesheets))
(use-modules (gnucash report report-system))
(define constructor (record-constructor <report>))
</syntaxhighlight>

2. Adding test-server.scm onto the CMakeFiles.txt in the same folder to enable compilation

3. Running make or ninja to generate the build directory

4. Running test-server.scm from the build directory by
<syntaxhighlight lang="sh">cd build/gnucash/report/standard-reports/test
/usr/bin/ctest -R test-server</syntaxhighlight>

This will run the test server.

5. Switch to another terminal, run
<syntaxhighlight lang="sh">nc localhost 37146 (the default guile port, upside down 37146 looks like guile...)
</syntaxhighlight>

This will now present a full Guile REPL prompt, with full access to the test-server.scm bindings as well as the Gnucash API. People familiar with emacs and the geiser package may also connect to the server by
<code>M-x connect-to-guile</code>. Unfortunately so far, only the environment is loaded. I do not think the file-load mechanism is accessible to scheme, which is an inconvenience for testing reports.

The developer can try:

<syntaxhighlight lang="scheme">
> ,apropos xacc [RET]
(sw_engine): xaccTransEqual	#<procedure xaccTransEqual (_ _ _ _ _ _)>
(sw_engine): xaccSplitGetCorrAccountCode	#<procedure xaccSplitGetCorrAccountCode (_)>
(sw_engine): xaccAccountGetReconciledBalance	#<procedure xaccAccountGetReconciledBalance (_)>
(sw_engine): xaccClearMarkDown	#<procedure xaccClearMarkDown (_ _)>
(sw_engine): xaccSplitSetBaseValue	#<procedure xaccSplitSetBaseValue (_ _ _)>
(sw_engine): xaccTransGetFirstAPARAcctSplit	#<procedure xaccTransGetFirstAP

etc

> ,apropos gnc- [RET]
(sw_engine): gnc-monetary-list-delete-zeros	#<procedure gnc-monetary-list-delete-zeros (_)>
(sw_engine): gnc-gdate-set-prev-fiscal-year-start	#<procedure gnc-gdate-set-prev-fiscal-year-start (_ _)>
(sw_engine): gnc-quote-source-get-internal-name	#<procedure gnc-quote-source-get-internal-name (_)>
(sw_engine): gnc-numeric-check	#<procedure gnc-numeric-check (_)>
(sw_engine): gnc-timegm	#<procedure gnc-timegm (_)>
(sw_engine): gnc-account-join-children	#<procedure gnc-account-join-c

etc

> ,bindings
constructor             #<variable 55cae1534b70 value: #<procedure 55cae11ff080 at ice-9/boot-9.scm:1340:17 (a b c d e f g h)>>
%module-public-interface #<variable 55cae0652da0 value: #<interface (guile-user) 55cae0638b40>>
run-test                #<variable 55cae1534cc0 value: #<procedure run-test ()>>

> (current-time)
1515297631

> (qof-print-date (current-time))
"07/01/18"

> (qof-date-format-set QOF-DATE-FORMAT-ISO)
> (qof-print-date (current-time))
"2018-01-07"

</syntaxhighlight>

== Other Resources ==

One other way to create custom reports outside GnuCash, but directly from GnuCash data, is to use [[Ledger-CLI]].
=== Old GnuCash Report Information ===
(may be very out of date)
* [http://www.gnucash.org/docs/v1.6/C/x4501.html Version 1.6 report documentation]
* [[FAQ#Q:_I.27d_like_to_write_my_own_custom_reports._Where_should_I_start.3F]]
* [https://lists.gnucash.org/pipermail/gnucash-devel/2001-May/003493.html From the mailing list]

=== Learning Scheme ===
* [http://groups.csail.mit.edu/mac/projects/scheme/ MIT Scheme Index]
* [http://download.plt-scheme.org/doc/360/html/t-y-scheme/t-y-scheme.html Teach Yourself Scheme in Fixnum Days]
* [http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-1.html Structure and Interpretation of Computer Programs]
* [http://www.htdp.org/  How to Design Programs] and [http://www.ccs.neu.edu/home/matthias/HtDP2e/ HtDP, 2nd Edition]
* [https://mitpress.mit.edu/books/little-schemer-fourth-edition The Little Schemer]
* Mastering Scheme is highly eased after reading [http://www.scheme.com/tspl4/ The Scheme Progamming Language] by R. Kent Dybvig
* [http://www.gnu.org/software/guile/docs/docs.html Guile documentation]
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