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Metal: clear bottom strip when minibuffer height changes (expose substitute)

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NS repaints uncovered regions through its drawRect: expose path; the
Metal overlay has none, so when a multi-line echo message shrank back,
stale pixels (e.g. a wrap-arrow shard in the echo fringe) survived.
Detect minibuffer pixel-height changes in update_begin and clear the
affected bottom strip inside the same update cycle, so the redraw and
the clear land in one present without flashing.
This commit is contained in:
Andros Fenollosa 2026-06-03 19:48:02 +02:00
parent 9c68084ac3
commit 52e46fa7a8
2 changed files with 28 additions and 0 deletions
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5
src/mtlterm.h
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@ -174,6 +174,11 @@ typedef struct mtl_spring {
the whole clear+redraw sequence is shown in one go (no flicker). */
@property (nonatomic, assign) BOOL needsPresent;
/* Expose substitute: last known pixel height of the minibuffer window. When it
changes, update_begin clears the affected bottom strip (NS relies on its
drawRect: expose path for the uncovered pixels; Metal has none). */
@property (nonatomic, assign) int lastMiniHeight;
/* Main Emacs render cycle (renders to staticTexture) */
- (void)beginFrame;
- (void)endFrame;

23
src/mtlterm.m
View file

@ -2703,6 +2703,29 @@ mtl_update_begin (struct frame *f)
end it cleanly before starting a new frame. */
if (fd.encoder) [fd endFrame];
[fd beginFrame];
/* Expose substitute: when the minibuffer (echo area) changes height, the
bottom of the layout shifts but the engine does not repaint every
uncovered pixel — it relies on an expose pass that NS gets via drawRect:
and Metal does not have. (Seen as a stale wrap-arrow shard in the echo
fringe after a multi-line message shrank back.) Clear the affected
bottom strip at the start of this same update; the update then redraws
the real rows on top, all within one present, so nothing flashes. */
if (WINDOWP (FRAME_MINIBUF_WINDOW (f)))
{
struct window *mini = XWINDOW (FRAME_MINIBUF_WINDOW (f));
int mh = WINDOW_PIXEL_HEIGHT (mini);
if (fd.lastMiniHeight > 0 && mh != fd.lastMiniHeight)
{
int maxh = mh > fd.lastMiniHeight ? mh : fd.lastMiniHeight;
int y0 = FRAME_PIXEL_HEIGHT (f) - maxh - FRAME_LINE_HEIGHT (f);
if (y0 < 0) y0 = 0;
[fd fillRect:NSMakeRect (0, y0, FRAME_PIXEL_WIDTH (f),
FRAME_PIXEL_HEIGHT (f) - y0)
color:ns_color_to_pixel (FRAME_BACKGROUND_COLOR (f))];
}
fd.lastMiniHeight = mh;
}
}
static void