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Metal: clip glyph strings with the engine clip rect (scissor)

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The NS backend clips every glyph string draw to
get_glyph_string_clip_rect via ns_focus; Metal drew unclipped. The most
visible casualty: a filled-box cursor on a tall row (e.g. a line with an
inline image) painted the cursor background over the full row height
(60px bar) instead of the character cell, because draw_phys_cursor_glyph
relies on the clip rect, narrowed to the physical cursor box, to bound
the DRAW_CURSOR background fill.

Apply the same rect as an MTLScissorRect around each glyph string draw
(applyClipRect:/clearClipRect on the static-texture encoder, mapped to
physical pixels and clamped), in both the in-cycle and immediate paths.
Also bounds overhang bleed into neighboring windows for free.

Verified: cursor on an image row now renders as a character-sized box
with the glyph inverted, identical to NS; baseline AE unchanged (0.068%).
This commit is contained in:
Andros Fenollosa 2026-06-03 17:47:39 +02:00
parent 6663cfcd5f
commit 6c7de3c114
1 changed files with 47 additions and 0 deletions
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47
src/mtlterm.m
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@ -1044,10 +1044,47 @@ easing_apply (MtlScrollEasing mode, float t)
- (void)shiftGlyphsX:(int)x y:(int)y width:(int)w height:(int)h by:(int)shift;
- (void)drawFringeBits:(unsigned short *)bits dh:(int)dh wd:(int)wd h:(int)h
atX:(int)x y:(int)y color:(unsigned long)color;
- (void)applyClipRect:(NSRect)r;
- (void)clearClipRect;
@end
@implementation MtlFrameData
/* Clip subsequent draws on the current encoder to R (logical pixels), like the
NS backend's ns_focus clipping with get_glyph_string_clip_rect. This is what
keeps a filled-box cursor on a tall row (e.g. an image line) at the size of
the character cell instead of the whole row, and stops overhangs from
bleeding outside the window area. */
- (void)applyClipRect:(NSRect)r
{
if (!self.encoder || !self.staticTexture) return;
CGSize dsz = self.metalLayer.drawableSize;
NSSize lsz = self.metalLayer.frame.size;
double scx = lsz.width > 0 ? dsz.width / lsz.width : 1.0;
double scy = lsz.height > 0 ? dsz.height / lsz.height : 1.0;
long tw = (long) self.staticTexture.width;
long th = (long) self.staticTexture.height;
long x0 = lround (NSMinX (r) * scx), y0 = lround (NSMinY (r) * scy);
long x1 = lround (NSMaxX (r) * scx), y1 = lround (NSMaxY (r) * scy);
if (x0 < 0) x0 = 0;
if (y0 < 0) y0 = 0;
if (x1 > tw) x1 = tw;
if (y1 > th) y1 = th;
if (x1 <= x0 || y1 <= y0)
{ x0 = tw - 1; y0 = th - 1; x1 = tw; y1 = th; } /* effectively clip out */
MTLScissorRect sc = { (NSUInteger) x0, (NSUInteger) y0,
(NSUInteger) (x1 - x0), (NSUInteger) (y1 - y0) };
[self.encoder setScissorRect:sc];
}
- (void)clearClipRect
{
if (!self.encoder || !self.staticTexture) return;
MTLScissorRect sc = { 0, 0, self.staticTexture.width,
self.staticTexture.height };
[self.encoder setScissorRect:sc];
}
/* Open a render command encoder targeting the static texture. CLEAR wipes it to
the frame background (only for a fresh/resized texture); otherwise LOAD
preserves the previous content (Emacs redraws just the dirty regions).
@ -2481,14 +2518,24 @@ mtl_draw_glyph_string (struct glyph_string *s)
state leak into the next click/redisplay. Committing per draw keeps the
pipeline clean, and deferring the present lets mtl_flush_display show the
whole sequence in one composite. */
/* Clip to the same rect the NS backend uses (window area; narrowed to the
physical cursor box for DRAW_CURSOR strings, which is what keeps the
filled-box cursor character-sized on tall image rows). */
NSRect clip;
get_glyph_string_clip_rect (s, &clip);
if (fd.encoder)
{
[fd applyClipRect:clip];
mtl_draw_glyph_string_impl (s);
[fd clearClipRect];
}
else
{
[fd beginFrame];
[fd applyClipRect:clip];
mtl_draw_glyph_string_impl (s);
[fd clearClipRect];
[fd endFramePresent:NO];
}
}