[PATCH v2 06/10] lib/fonts: Refactor glyph-pattern helpers

Thomas Zimmermann
2026-04-07T09:26:09Z

Change the signatures of the pattern helpers to align them with other
font-glyph helpers: use the font_glyph_ prefix and pass the glyph
buffer first.

Calculating the position of the involved bit is somewhat obfuscated
in the original implementation. Move it into the new helper
__font_glyph_pos() and use the result as array index and bit position.

Note that these bit helpers use a bit pitch, while other code uses a
byte pitch. This is intentional and required here.

v2:
- fix typos in commit message

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
lib/fonts/font_rotate.c | 45 ++++++++++++++++++++++++-----------------
1 file changed, 27 insertions(+), 18 deletions(-)

diff --git a/lib/fonts/font_rotate.c b/lib/fonts/font_rotate.c
index d107a8d0a2b0..d79ec5eef712 100644
--- a/lib/fonts/font_rotate.c
+++ b/lib/fonts/font_rotate.c
@@ -15,21 +15,33 @@

#include "font.h"

-static inline int pattern_test_bit(u32 x, u32 y, u32 pitch, const char *pat)
+static unsigned int __font_glyph_pos(unsigned int x, unsigned int y, unsigned int bit_pitch,
+ unsigned int *bit)
{
- u32 tmp = (y * pitch) + x, index = tmp / 8, bit = tmp % 8;
+ unsigned int off = y * bit_pitch + x;
+ unsigned int bit_shift = off % 8;

- pat += index;
- return (*pat) & (0x80 >> bit);
+ *bit = 0x80 >> bit_shift; /* MSB has position 0, LSB has position 7 */
+
+ return off / 8;
}

-static inline void pattern_set_bit(u32 x, u32 y, u32 pitch, char *pat)
+static bool font_glyph_test_bit(const unsigned char *glyph, unsigned int x, unsigned int y,
+ unsigned int bit_pitch)
{
- u32 tmp = (y * pitch) + x, index = tmp / 8, bit = tmp % 8;
+ unsigned int bit;
+ unsigned int i = __font_glyph_pos(x, y, bit_pitch, &bit);
+
+ return glyph[i] & bit;
+}

- pat += index;
+static void font_glyph_set_bit(unsigned char *glyph, unsigned int x, unsigned int y,
+ unsigned int bit_pitch)
+{
+ unsigned int bit;
+ unsigned int i = __font_glyph_pos(x, y, bit_pitch, &bit);

- (*pat) |= 0x80 >> bit;
+ glyph[i] |= bit;
}

static inline void rotate_cw(const char *in, char *out, u32 width, u32 height)
@@ -42,9 +54,8 @@ static inline void rotate_cw(const char *in, char *out, u32 width, u32 height)

for (i = 0; i < h; i++) {
for (j = 0; j < w; j++) {
- if (pattern_test_bit(j, i, width, in))
- pattern_set_bit(height - 1 - i - shift, j,
- height, out);
+ if (font_glyph_test_bit(in, j, i, width))
+ font_glyph_set_bit(out, height - 1 - i - shift, j, height);
}
}
}
@@ -81,10 +92,9 @@ static inline void rotate_ud(const char *in, char *out, u32 width, u32 height)

for (i = 0; i < height; i++) {
for (j = 0; j < width - shift; j++) {
- if (pattern_test_bit(j, i, width, in))
- pattern_set_bit(width - (1 + j + shift),
- height - (1 + i),
- width, out);
+ if (font_glyph_test_bit(in, j, i, width))
+ font_glyph_set_bit(out, width - (1 + j + shift),
+ height - (1 + i), width);
}
}
}
@@ -119,9 +129,8 @@ static inline void rotate_ccw(const char *in, char *out, u32 width, u32 height)

for (i = 0; i < h; i++) {
for (j = 0; j < w; j++) {
- if (pattern_test_bit(j, i, width, in))
- pattern_set_bit(i, width - 1 - j - shift,
- height, out);
+ if (font_glyph_test_bit(in, j, i, width))
+ font_glyph_set_bit(out, i, width - 1 - j - shift, height);
}
}
}
--
2.53.0