Wrong value of TDrawGrid's Canvas.font.height

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Author Topic: Wrong value of TDrawGrid's Canvas.font.height (Read 310 times)

jdp1024

Newbie
Posts: 1

Wrong value of TDrawGrid's Canvas.font.height

« on: February 03, 2025, 04:38:22 pm »

I am a user of Double Commander which uses TDrawGrid as the file list and TPageControl to switch between multiple lists. I use it under Windows 11 23H2.

When I tried to change the font of the TPageControl, I found the font height of the TDrawGrid is slightly larger than expected under a high DPI display. With a display with 200% scale (192 DPI), when Font.Size is 8, the expected height is -21 (8*192/72=21.33), but the actual value is -22. With a display with 350% scale (336 DPI), the expected height is -37 (8*336/72=37.33), but the actual value is -39.

This only happens when DesignTimePPI is not specified.

I can confirm that it is not a bug of Double Command but a bug of LCL. I have created a minimal project to reproduce the problem. Anyone please give me some hint of how and where the Height value of the font is calculated. I have checked grids.pas and font.inc but I can't see what is wrong. Thanks in advance.