LMD 2009 - Theme Engine

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From LMD-Tools 2009 releases we introduce new approach to Theme Engine. This approach aims at following main goals:

  • Basic theme engine causes no or only small overhead (by using System Themes support of Delphi, which is integrated since Delphi 7);
  • Management of any calls for internal theme services is centralized;
  • No theme related switches and recompilation of library code, but a separate package which you can decide to use or not at runtime;
  • Possibility of using custom theme and system theme simultaneously.

The entry point for new theme services is now LMDThemes unit.
This unit introduces TLMDThemeRenderer and TLMDThemeServices classes, LMDThemeServices (global method to access a singleton instance of TLMDThemeServices class), some helper methods like LMDSetThemeMode, and a number of theme related constants.
TLMDThemeRenderer class is an abstract ancestor class for any custom theme renderers.
TLMDThemeServices class provides centralized and unified access to theme rendering routines.

Changes from LMD-Tools 2007 version of theme services

General changes

LMDXPStyles and LMDXPThemeManager units removed.
Wherever it is possible, system Themes and UxTheme units are used.
CtlXP property is now deprecated (moved to public), it is no longer used and remains only for compatibility reasons. ThemeMode (of TLMDThemeMode type, defined in LMDClass unit) property introduced to be used instead of CtlXP.
Type TLMDThemeMode = (ttmNone, ttmPlatform, ttmNative):
ttmNone = No global themeing, use control settings
ttmPlatform = CtlXP or UseXPThemes
ttmNative = our native theme engine
The intfThemes unit is now deprecated.
LMDSetCtlXP helper method, which was defined in intfThemes, is replaced by LMDSetThemeMode, defined in LMDThemes unit:

procedure LMDSetThemeMode(aParent: TWinControl; const Value: TLMDThemeMode);overload;
 procedure LMDSetThemeMode(aParent: TCustomForm; const Value: TLMDThemeMode);overload;

The call

LMDSetCtlXP (self, true);

must be replaced by

LMDSetThemeMode(self, ttmPlatform);

The call like

LMDSetCtlXP (self, false);

must be replaced by

LMDSetThemeMode(self, ttmNone);

Changes to component code

A standard example for replacing code:

 if UseXP or (LMDApplication.UseXPThemes and (Bevel.Mode=bmWindows)) then
     aPartId&nbsp;:= PP_BAR;
     if Direction in [mdVertical, mdVerticalReverse] then
        aPartId&nbsp;:= PP_BARVERT;
     DrawThemeBackGround (LMDThemeService.Theme[tiProgress], Canvas.Handle, aPartId, 0, FRect, nil);
     {$ifdef CLR}
     GetThemeBackgroundContentRect (LMDThemeService.Theme[tiProgress], Canvas.Handle, aPartId, 0, FRect, FRect);
     {$else ifdef CLR}
     GetThemeBackgroundContentRect (LMDThemeService.Theme[tiProgress], Canvas.Handle, aPartId, 0, FRect, {$IFDEF LMDDISABLE_LMDTHEMES}@{$ENDIF}FRect);
     {$endif ifdef CLR}
changes now to:
 lThemeMode&nbsp;:= UseThemeMode; // store current ThemeMode locally when it is used more than once
 if (lThemeMode &lt;&gt; ttmNone) then // same as IsThemed, because UseThemeMode was already determined, this is faster 
     if Direction in [mdVertical, mdVerticalReverse] then
        Details&nbsp;:= tpBarVert
        Details&nbsp;:= tpBar;
     LMDThemeServices.DrawElement(lThemeMode, Canvas.Handle, Details, FRect);
     FRect&nbsp;:= LMDThemeServices.ContentRect(lThemeMode, Canvas.Handle, ThemeServices.GetElementDetails(Details), FRect);

As one can see, code becomes much more cleaner and readable. Notes:

  • All ThemeModes <> ttmNone are handled by LMDThemeServices.
  • UseThemeMode takes care to check whether a specific thememode is available. It will automatically provide least possible theme mode, e.g. ttmNone on Win98 systems if ThemeMode = ttmPlatform.
  • Take GlobalThemeMode into account. GlobalThemeMode allows programmer to change ThemeMode for complete application with one boolean property.
  • LMDApplication.UseXPThemes is only available for compatibility, never use it in new code (use LMDThemeService methods)
  • Use LMDPtrToRect, LMDRectToPtr methods for PRect/IntPtr variables (to avoid {$IFNDEF CRL}@{$ENDIF} code).

Changes to native theme engine

Native theme engine is available now as a standalone package LMD Themes Pack. No compiler switches are needed to enable/disable native theme engine.
Components TLMDThemeEngineController and TLMDFormThemeProvider moved to LMD Themes Pack. Theme engine can load only one theme at a time, LoadTheme methods removed. This allowed to simplify code greately.
TLMDThemeEngine is now a descendand of TLMDThemeRenderer class.
ActivateColorScheme method added:

function ActivateColorScheme(ColorScheme: WideString = ''): boolean;

TLMDThemeEngine methods return (where applicable) boolean values (true if succeeded, false if failed) instead of HRESULT values.
Note: The behaviour of ActivateThememethod changed. In previous version, if LMDThemeEngine.Enabled was false, then ActivateTheme failed. In new version, ActivateTheme method can be called even if theme engine is disabled, and, if succeeded, it activates theme engine, too.