Wednesday, May 13, 2009

Changes with Button Glyphs

If you ever worked with the Lazarus IDE under windows (or just compiled an LCL application for windows) you were probably sickened by the glyphs on the dialog buttons since it is not native for windows. But on linux all is vice versa - most of the buttons have glyphs (and for example gtk and qt suggest an appropriate API to query "stock" images for buttons with various actions like save, open, apply, cancel, ...).
Therefore I needed a solution which can satisfy both windows and linux users. I started from the TBitBtn class which represents a button control with an image inside it. What I have added is a new property "GlyphShowMode" with 4 states:
  • gsmAlways
  • gsmNever
  • gsmApplication
  • gsmSystem
It is clear what the gsmAlways and gsmNever states are for: gsmAlways - to show the glyph always and this is how it worked before, gsmNever - to show the glyph never. Well, you may ask: What do I need the gsmNever state for, if I can use a TButton instead?. And I would answer: TBitBtn is not just a button with an image. It also has a Kind property which is very useful to set the ModalResult and Caption of a button :) But let's return to the other modes. gsmSystem can be used to show glyph depending on current OS - on MS Windows glyph will not be shown and on other system it will. And the last mode which is also default for this property - gsmApplication. In this mode TBitBtn (well, not exactly TBitBtn but TButtonGlyph) will look at the Application object for its value.
So, you can control the visibility of all button glyphs using the Application object. How? There are 2 ways: at run time by changing the Application.ShowButtonGlyphs property or at design time by changing the same property for the TApplicationProperties component. TShowButtonGlyphs is an enumeration too with following elements similar to TGlyphShowMode:
  • sbgAlways
  • sbgNever
  • sbgSystem
The default value for the ShowButtonGlyphs property is sbgAlways and not sbgSystem as one may expect. The reason is compatibility with old applications. Developers don't like surprises after a development tool upgrade and the loss of images is not a nice surprise. Anyway, it is not difficult to change the behavior of your application.
One more thing - glyphs are always visible when you are designing your forms. The glyph visibility mode is applied to the controls only at run time (when you start your application).

And now with regards to the Lazarus IDE. After this change the IDE on windows does not show glyphs on buttons by default, but if you really liked them, you can ask IDE to return them. You need to open the IDE options dialog and select Desktop settings: