kcms/fonts: Fix font hinting preview
In combineImages, the width and the height were calculated
incorrectly. This makes the preview image correctly obey the device
pixel ratio of the primary screen, so the preview image can be clear
and sharp.
BUG: 413673 FIXED-IN: 5.25.0
Ref: plasma-desktop#34 (closed)
| Before (125% scale) | After (125% scale) | After multiline (125% scale) |
|---|---|---|
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| Before (200% scale) | After (200% scale) |
|---|---|
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Edited by Fushan Wen