Adds gfx_printBufferClipped: a variant of gfx_printBuffer that accepts
an explicit right-edge limit (max_x) and a vertical clip window
[clip_top_y, clip_bot_y]. Word-wrap fires when the next glyph would
exceed max_x. Pixels outside the clip window are suppressed without
affecting layout, so a negative start.y can be used to implement smooth
text scrolling.
gfx_printBuffer now delegates entirely to gfx_printBufferClipped with
clip_top_y=0 and clip_bot_y=CONFIG_SCREEN_HEIGHT-1. The old pixel guard
used strict > 0 comparisons, which excluded pixels at row 0 and column 0.
The new implementation renders those pixels; callers that relied on the
old exclusion will see a behaviour change.
Compared to a naive port of gfx_printBuffer, this implementation
addresses several correctness issues:
- Control characters '\n' and '\r' are checked before the glyph array
is indexed, avoiding undefined behaviour on fonts whose first codepoint
is at or above 0x20 (e.g. TomThumb, first=0x20), since '\n' (0x0A)
would produce a negative index.
- get_line_size uses <= instead of < when accumulating glyph widths so
that a glyph whose xAdvance exactly equals max_width is counted. The
render loop uses strict > to trigger wrap, so the old < mismatch caused
text_size.x to be under-reported by one glyph whenever a line was an
exact fit, and misplaced CENTER/RIGHT lines in that case.
- For TEXT_ALIGN_LEFT, line_size is recomputed on every '\n' before the
max_line_size comparison. Without this, max_line_size was stuck at the
first-line width for the entire call, so text_size.x was wrong whenever
a subsequent line was wider.
- saved_start_y is int16_t to match point_t.y, allowing correct
text_size.y computation when start.y is negative (scroll offset).
- text_size.y is computed as (start.y - saved_start_y) + line_h,
matching the sign fix introduced for gfx_printBuffer.
- Pixels above row 0 (py < 0) are suppressed before the uint16_t cast
passed to gfx_setPixel, preventing a silent wrap to a large row index.
- max_line_size tracks the widest line across all line breaks and wraps;
text_size.x reflects the widest line, not just the last.
Extend tests/unit/gfx_text.cpp with return-value tests covering:
single-line height, two-line height delta equals yAdvance, negative
start.y scroll offset, negative clip_top_y, exact-fit line width
(get_line_size <= boundary), max line width from a wider first line,
max line width from a wider second line (TEXT_ALIGN_LEFT regression),
glyph at clip_bot_y not skipped, and TEXT_ALIGN_RIGHT per-line reset.
Co-authored-by: GitHub Copilot <copilot@github.com>
Signed-off-by: Ryan Turner <ryan@turnrye.com>
Refactor the static helper get_line_size to accept an explicit max_width
parameter instead of the hardcoded CONFIG_SCREEN_WIDTH cap. All three
call sites in gfx_printBuffer are updated to pass CONFIG_SCREEN_WIDTH,
preserving existing behaviour.
Add gfx_measureText: a pure-computation function that simulates the same
word-wrap pass as gfx_printBufferClipped (to be added next) without
touching the display. It returns the total pixel height of the laid-out
text block and accepts a char_count limit so callers can compute the
y-coordinate of an arbitrary cursor position for scroll-offset
calculations.
Add tests/unit/gfx_text.cpp and register the gfx_text_test executable in
meson.build. The test suite covers single-line strings, multi-line
strings via explicit newlines, char_count truncation, and word-wrap
height growth.
Co-authored-by: GitHub Copilot <copilot@github.com>
Signed-off-by: Ryan Turner <ryan@turnrye.com>
