TToolbar incompatible with TForm.DoubleBuffered?
delphi, delphi-xe3, doublebuffered, toolbar, vcl
Solution
In my opinion the solution is to set `TForm.DoubleBuffered` to `False`. Using a value of `True` causes all sorts of other problems. This property worked reasonably well before XP themes, but since their arrival, using `TForm.DoubleBuffered` has not been viable, in my view.
In addition to the problems you have encountered, I've come across lots of painting flaws when using the Windows Basic theme. I know that's not mainstream, but I happen to see that a lot with remote access. And there's more. When you double buffer a form you stop the theme animation from working. For example, a default button pulses to indicate that it is the default button.
If you get resize flickering without double buffering the form, use the ideas from my answer to another question. From the comments it seems that the flickering you wish to combat is in a paint box. I obviously don't know the details, but my experience and instincts say that you should be able to deal quite easily with that flickering at a local level. There surely should be no need for the global form wide double buffering.
Problem
I am using Delphi XE3. When I create a new VCL project and drop a `TToolbar` on it, everything works fine - except when I activate `Form1.DoubleBuffered`. From that moment on, drawing of the toolbar is broken - in designtime, it's either black, transparent, or parts of the IDE (statusbar, toolbar, etc.) are copied into it. It changes between these options when I click on it and when I change to source code (F12) and back. In runtime, it's always black. With `DrawingStyle=dsGradient`, everything works as expected. Switching back to `dsNormal` breaks it again. Deactivating `Form1.DoubleBuffered` repairs it. Any hints how to work around that issue?