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4fa51b950c
After a roundabout discussion[1] with wlroots devs, it's become apparent that subpixel text rendering (a.k.a. "ClearType") does not work properly when rendering over a transparent background, as labwc currently does. Basically it comes down to the fact that the color of semi-transparent pixels (which is adjusted redder or bluer to compensate for RGB subpixel alignment) depends somewhat on background color. When rendering over transparency, the text engine doesn't know the intended background color and can't adjust the pixel colors correctly. With Pango/Cairo, the end result can range from grayscale rendering (no subpixel rendering at all) to wrong/oversaturated colors (for example, bright pink pixels when rendering white text on blue background). This change solves the issue by first filling the text buffer with an opaque background color before rendering the text over it. Currently, this is easy since the background is always a solid color. It may be a little more complex (but doable) if we implement gradients in future. Note that GTK 4 (and to some degree, recent versions of Microsoft Windows) avoid this issue by disabling subpixel rendering altogether. I would much prefer that labwc NOT do this -- it results in noticeably blurrier text on non-retina LCD screens, which are still common. [1] https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3822
58 lines
1.4 KiB
C
58 lines
1.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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#ifndef LABWC_FONT_H
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#define LABWC_FONT_H
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struct lab_data_buffer;
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enum font_slant {
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FONT_SLANT_NORMAL = 0,
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FONT_SLANT_ITALIC
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};
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enum font_weight {
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FONT_WEIGHT_NORMAL = 0,
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FONT_WEIGHT_BOLD
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};
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struct font {
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char *name;
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int size;
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enum font_slant slant;
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enum font_weight weight;
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};
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struct _PangoFontDescription *font_to_pango_desc(struct font *font);
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/**
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* font_height - get font vertical extents
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* @font: description of font including family name and size
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*/
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int font_height(struct font *font);
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/**
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* font_width - get font horizontal extents
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* @font: description of font including family name and size
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*/
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int font_width(struct font *font, const char *string);
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/**
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* font_buffer_create - Create ARGB8888 lab_data_buffer using pango
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* @buffer: buffer pointer
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* @max_width: max allowable width; will be ellipsized if longer
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* @text: text to be generated as texture
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* @font: font description
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* @color: foreground color in rgba format
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* @bg_color: background color in rgba format
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* @arrow: arrow (utf8) character to show or NULL for none
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*/
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void font_buffer_create(struct lab_data_buffer **buffer, int max_width,
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const char *text, struct font *font, const float *color,
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const float *bg_color, const char *arrow, double scale);
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/**
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* font_finish - free some font related resources
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* Note: use on exit
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*/
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void font_finish(void);
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#endif /* LABWC_FONT_H */
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