Lazarus 3.0 release notes

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Revision as of 02:00, 19 September 2022 by Martin (talk | contribs) (→‎Debugger)
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Lazarus 2.4.0 is not yet released. This page is under construction!


  1. commits: xxx
  2. log: svn log -r xxxx:xxxx
  3. resolved bug tracker issues: xxx

LCL Interfaces Changes

LCL Changes


  • Old behaviour Win32: A placeholder icon was used for FooterIcon = tdiNone and MainIcon = tdiNone.
  • New behaviour Win32: No icon is used for FooterIcon = tdiNone and MainIcon = tdiNone.
  • Reason: Removing drawing glitch. The text move over to allow more content and better alignment. See Issue #39172


  • Old behaviour: Multi-line captions could only be entered by code. And multi-line captions were always left-aligned.
  • New behaviour: Multi-line captions can also be entered in the object inspector. New property Alignment to specify whether the caption should be left-/right-aligned or centered. Default: centered, like in Delphi.
  • Reason: Better usability.

TLabel.Transparent, .Color and .ParentColor changes

  • Old behaviour: Transparent property was bound to Color=clNone
  • New behaviour: Transparent is a standalone property
  • Reason: Delphi compatibility and to fix ParentColor issues.
  • Remedy: If you are setting the Color property, Transparent is not automatically switched from True to False now, you have to do it yourself. This is in compliance with Delphi and also solves problems with Color/ParentColor changes.


  • Old behaviour: The panel caption was always centered vertically.
  • New behaviour: The new property VerticalAlignment (taAlignTop, taAlignBottom, taVerticalCenter) allows to place the caption also at the top or bottom of the panel interior.
  • Reason: Delphi compatibility and better usability


  • Properties MinDate and MaxDate are implemented. These limits are only imposed if MaxDate > MinDate. Unfortunately GTK2/3 widgetsets do not support this, so selecting a date outside the MinDate/MaxDate range will still be possible there.

TCheckbox, TRadioButton

  • Different calculation of checkbox/radiobutton size in order to correctly take care of Win-10 "ease of access" feature. See Issue #39398
  • Consequence: lfm files will contain different sizes of these controls (if auto-sized) compared with earlier versions.

IDE Changes

Character map

  • Resizable characters to improve readability.


  • Improved Watches window
    • Expand/Unfold for classes, records, etc
    • Expand/Unfold with paged browser for arrays
    • Drag and Drop to reorder watches
    • Drag and Drop to create new "top level" watches from nested entries (in expand/unfolded lists)
    • Address column for types with internal pointer (classes, long-string, dyn-array, (real) pointer)
  • Improved Inspect window
    • Fixed: Updating value when context changes
    • Added options for Function calling / and "Converter" (See FpDebug: SysVarToLstr)
  • Improved Evaluate/Modify window
    • New Layout
    • Added DisplayFormat
    • Added options for Function calling / and "Converter" (See FpDebug: SysVarToLstr)
  • Per project "Debugger backend" settings. In addition to choosing a specific backend from the global IDE settings, a backend can be configured just for the project (i.e. special gdb-server settings)


  • Improved "function calling" in watch eval. See FpDebug-Watches-FunctionEval
  • %RAX Accessing cpu registers in watch expression (only full registers, not yet AH or AL or EAX on 64bit)
  • Intrinsic functions: FpDebug-Watches-Intrinsic-Functions
  • Option to detect "variant" and call "SysVarToLStr" in the target app.
  • Suspend/Resume individual threads (must be done while app is paused, and will be applied for subsequent step/run)

IDE Interface Changes



  • The TLegendClickTools now is able to detect clicks on series legend items and reports the clicked series in the new OnSeriesClick event.
  • New TDatapointMarksClickTool which becomes active when the user clicked on the marks of a series.
  • New property TickWidth for the chart axes.
  • New property RandomColors for TRandomChartSource.
  • New properties YIndexWhiskerMin, YIndexBarMin, YIndexCenter, YIndexBarMax, YIndexWhiskerMax, and YDataLayout in TBoxAndWhiskerSeries for more flexible assignment of y values to the parts of the box/whisher shape.


  • lazbuild now can compile pas2js projects by passing the environment variable PAS2JS with the path of the pas2js executable.
  • Project groups with pas2js projects now can compile without being opened.
  • New project type Progressive Web Application
  • New project type Electron Web Application
  • pas2jsdsgn now uses the SimpleWebServerGUI package, replacing its own http server controller.
  • F9, Run now builds, starts a HTTP server and a browser

Lazarus Icon Collection

  • Not a component, but the Lazarus installation now contains a folder with general-purpose icons for usage in toolbars, menus, buttons etc. of any GUI applications (folder images/general_purpose).
  • The images come in various sizes and thus are compatible with the scaled image list of Lazarus v2.0+.
  • Author: Roland Hahn
  • License: Creative Commons CC0 (no restrictions in usage).

Changes affecting compatibility



The value of NullDate has changed.

  • It was impssible to actually select the date corresponding to NulDate (30 dec 1899 by default) in the control.
  • Remedy (1): if your code depended on NullDate actually being 0.0, you have to adjust your code.
  • Remedy (2): if your code used NullDate for a TTimeEdit, change that to the new constant NullTime instead.
  • Note: NullDate is actually a writeable constant. This was kept for compatibility reasons. It is however a bad idea to change it's value to anything that is an actual date that is withing the range of the control.


Masks unit

The masks unit has been completely rewritten.

  • speed: the old Matches() method had O(n^2) or even O(n^3) characteristics.
  • improved control over how the mask is interpreted.

New types (for parameters) and a dedicated TMaskWindows class have been added.
TMask.MatchesWindowsMask and the old TMaskOptions type have been deprecated and will be removed in the next release.

Ranges and Sets
  • The old masks implementation supported sets, but not ranges. The new implementation supports both sets ([abc]) and ranges ([a-c]). As a consequence a '-' inside such a construct is now interpreted as part of the range definition, not as a literal '-'.
  • Reason: ranges are a good thing to have by default (the old implementation simply lacked this). We decided it's a small price to pay.
  • Remedy: either escape the '-' with EscapeChar (which defaults to '\') or exclude mocRange from the TMaskOpcodes parameter.
Constructors do not fail anymore on an invalid mask
  • When providing an invalid mask to the old T(Windows)Mask(List) constructors an exception was raised.
  • The new constructors do not raise an exception in this case. Instead an exception is raised in when Matches() is called.
  • Reason: it's not very nice to have a constructor fail.

Components incompatibility


  • The property NumbersOnly is no longer published.
  • Reason: the property makes no sense for this control and only confuses users.
  • Remedy: if you really need NumbersOnly to be True, you must set it in code.

Other release notes