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Hello Lazarus mailing list!
I am still porting our application from Delphi/Kylix to Lazarus and
the performance of the same units responsible for graphical output are
nearly the same, but the performance on Lazarus Carbon/Gtk2 is much
slower than on VCL/CLX.
1. The gtk drawing functions are per se slower than the winapi functions.
2. To achieve Delphi compatible drawing the LCL has to combine several gtk functions to get the same effect of one winapi function. Especially the specialized functions, that are fast under winapi, have no direct counterpart in the gtk. And Delphi programs use mostly the fast functions of the winapi.
3. system colors (e.g. clBtnFace) are gradients and images under gtk, while under winapi they are simple colors.
What would you recommend to find out the bottleneck of the
performance. Maybe it is in some part of code about painting which
must be rewritten for performance improvement on LCL.
Try to reduce the number of drawing operations. For example don't use Get/SetPixel. Use a polygon instead of MoveTo/LineTo. Use default fonts and text styles. Use default Brush and Pen styles. Draw to a memory bitmap and draw that. See my other mail about fpcanvas and aggpas.
There are plans to accelerate aggpas by drawing directly to the widgetset image buffers.
Use gprof to find out where the bottleneck is.
Thanks for all recommendations in advance.
Mattias
