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modesetting: Handle reflected/rotated cursors better

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Moved the cursor glyph cropping into a separate function that handles reflections and rotations.

Also, x/y are indexes into the buffer, so they should be clamped to width/height len - 1 for correctness.

Signed-off-by: John Studnicka <contact@zentec.dev>
This commit is contained in:
John Studnicka
2026-01-28 22:26:54 -07:00
committed by Enrico Weigelt
parent 1a9d075b9a
commit 8fa58d3b51
1 changed files with 113 additions and 34 deletions
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147
hw/xfree86/drivers/video/modesetting/drmmode_display.c
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@@ -1857,13 +1857,10 @@ drmmode_set_cursor_position(xf86CrtcPtr crtc, int x, int y)
{
drmmode_crtc_private_ptr drmmode_crtc = crtc->driver_private;
drmmode_ptr drmmode = drmmode_crtc->drmmode;
Rotation rotation = crtc->rotation;
/* Core handles rotation; we only compensate for the cropped source window. */
if (rotation != RR_Rotate_0) {
x += drmmode_crtc->cursor_src_x;
y += drmmode_crtc->cursor_src_y;
}
/* Core handles rotation; we only compensate when the glyph box is offset from its click hotspot. */
x += drmmode_crtc->cursor_src_x;
y += drmmode_crtc->cursor_src_y;
drmModeMoveCursor(drmmode->fd, drmmode_crtc->mode_crtc->crtc_id, x, y);
}
@@ -1956,6 +1953,99 @@ drmmode_cursor_get_pitch(drmmode_crtc_private_ptr drmmode_crtc, int idx)
return drmmode_crtc->cursor_pitches[idx];
}
/*
* The core stores a single rotated/reflected cursor glyph inside a fixed-size
* cursor image buffer. The glyph is written into one corner depending on the
* screen rotation and reflections. We compute the bounding box of that placed
* glyph to crop just the relevant region.
*
* This is the placement of the cursor glyph for each screen rotation:
*
* +-----------+-----------+
* | Rotate 0 | Rotate 270|
* |(top-left) |(top-right)|
* +-----------+-----------+
* | Rotate 90 | Rotate 180|
* |(bot-left) |(bot-right)|
* +-----------+-----------+
*
* Reflections flip the corresponding coordinate before rotation:
* RR_Reflect_X mirrors across the Y axis (flips X), RR_Reflect_Y mirrors across
* the X axis (flips Y). This changes which corner the glyph occupies.
*/
static void
drmmode_transform_box_back(Rotation rotation, int image_width, int image_height,
int box_width, int box_height,
int *x_dst, int *y_dst,
int *dst_width, int *dst_height)
{
int dst_min_x, dst_min_y, dst_max_x, dst_max_y;
/* We want to get the (0,0) coordinates of the cursor glyph box. */
int src_min_x = 0;
int src_max_x = box_width - 1;
int src_min_y = 0;
int src_max_y = box_height - 1;
/* Reflect first, then rotate to match the logic in xf86_crtc_rotate_coord_back(). */
if (rotation & RR_Reflect_X) {
/* (x, y) -> (W - 1 - x, y) */
int rx_min = image_width - 1 - src_max_x;
int rx_max = image_width - 1 - src_min_x;
src_min_x = rx_min;
src_max_x = rx_max;
}
if (rotation & RR_Reflect_Y) {
/* (x, y) -> (x, H - 1 - y) */
int ry_min = image_height - 1 - src_max_y;
int ry_max = image_height - 1 - src_min_y;
src_min_y = ry_min;
src_max_y = ry_max;
}
switch (rotation & 0xf) {
case RR_Rotate_90:
/* (x, y) -> (y, W - 1 - x) */
dst_min_x = src_min_y;
dst_max_x = src_max_y;
dst_min_y = image_width - 1 - src_max_x;
dst_max_y = image_width - 1 - src_min_x;
break;
case RR_Rotate_180:
/* (x, y) -> (W - 1 - x, H - 1 - y) */
dst_min_x = image_width - 1 - src_max_x;
dst_max_x = image_width - 1 - src_min_x;
dst_min_y = image_height - 1 - src_max_y;
dst_max_y = image_height - 1 - src_min_y;
break;
case RR_Rotate_270:
/* (x, y) -> (H - 1 - y, x) */
dst_min_x = image_height - 1 - src_max_y;
dst_max_x = image_height - 1 - src_min_y;
dst_min_y = src_min_x;
dst_max_y = src_max_x;
break;
default:
/* RR_Rotate_0 or unknown rotation: identity */
/* (x, y) -> (x, y) */
dst_min_x = src_min_x;
dst_max_x = src_max_x;
dst_min_y = src_min_y;
dst_max_y = src_max_y;
break;
}
/* Clamp to the source image bounds. */
dst_min_x = MAX(dst_min_x, 0);
dst_min_y = MAX(dst_min_y, 0);
dst_max_x = MIN(dst_max_x, image_width - 1);
dst_max_y = MIN(dst_max_y, image_height - 1);
*x_dst = dst_min_x;
*y_dst = dst_min_y;
*dst_width = dst_max_x - dst_min_x + 1;
*dst_height = dst_max_y - dst_min_y + 1;
}
static void
drmmode_paint_cursor(struct dumb_bo *cursor_bo, int cursor_pitch, int cursor_width, int cursor_height,
const CARD32 * restrict image, int image_width, int image_height,
@@ -1967,6 +2057,10 @@ drmmode_paint_cursor(struct dumb_bo *cursor_bo, int cursor_pitch, int cursor_wid
CARD32 *cursor = cursor_bo->ptr;
/* Clamp to the source image bounds to avoid pointer UB and OOB reads. */
src_x = MAX(MIN(src_x, image_width - 1), 0);
src_y = MAX(MIN(src_y, image_height - 1), 0);
/*
* The image buffer can be smaller than the cursor buffer.
* This means that we can't clear the cursor by copying '\0' bytes
@@ -1978,8 +2072,7 @@ drmmode_paint_cursor(struct dumb_bo *cursor_bo, int cursor_pitch, int cursor_wid
drmmode_crtc->cursor_glyph_height == 0) ||
/* If cached glyph dimensions exceed the current crop window, force a full clear */
(src_x < 0 || src_y < 0 ||
drmmode_crtc->cursor_glyph_width > image_width - src_x ||
(drmmode_crtc->cursor_glyph_width > image_width - src_x ||
drmmode_crtc->cursor_glyph_height > image_height - src_y) ||
/* If the pitch changed, the memory layout of the cursor data changed, so the buffer is dirty */
@@ -2003,11 +2096,9 @@ drmmode_paint_cursor(struct dumb_bo *cursor_bo, int cursor_pitch, int cursor_wid
width_todo = MAX(drmmode_crtc->cursor_glyph_width, glyph_width);
height_todo = MAX(drmmode_crtc->cursor_glyph_height, glyph_height);
/* Clamp to the source image bounds to avoid OOB reads. */
src_x = MIN(MAX(src_x, 0), image_width);
src_y = MIN(MAX(src_y, 0), image_height);
width_todo = MIN(width_todo, image_width - src_x);
height_todo = MIN(height_todo, image_height - src_y);
/* Basic buffer bounds checking */
width_todo = MAX(MIN(width_todo, image_width - src_x), 0);
height_todo = MAX(MIN(height_todo, image_height - src_y), 0);
/* remember the size of the current cursor glyph */
drmmode_crtc->cursor_glyph_width = glyph_width;
@@ -2035,8 +2126,11 @@ drmmode_load_cursor_argb_check(xf86CrtcPtr crtc, CARD32 *image)
drmmode_crtc_private_ptr drmmode_crtc = crtc->driver_private;
modesettingPtr ms = modesettingPTR(crtc->scrn);
CursorPtr cursor = xf86CurrentCursor(crtc->scrn->pScreen);
const Rotation rotation = crtc->rotation;
int glyph_width = cursor->bits->width;
int glyph_height = cursor->bits->height;
int crop_width = glyph_width;
int crop_height = glyph_height;
if (drmmode_crtc->cursor_up) {
/* we probe the cursor so late, because we want to make sure that
@@ -2083,25 +2177,10 @@ drmmode_load_cursor_argb_check(xf86CrtcPtr crtc, CARD32 *image)
int src_x = 0;
int src_y = 0;
/* Crop origin matches the core's rotated cursor placement in the cursor image buffer. */
switch (crtc->rotation & 0xf) {
case RR_Rotate_0:
src_x = 0;
src_y = 0;
break;
case RR_Rotate_90:
src_x = 0;
src_y = image_height - glyph_height;
break;
case RR_Rotate_180:
src_x = image_width - glyph_width;
src_y = image_height - glyph_height;
break;
case RR_Rotate_270:
src_x = image_width - glyph_width;
src_y = 0;
break;
}
/* Map the source glyph box (0,0) into the displayed cursor image; src_x/src_y become BO (0,0). */
drmmode_transform_box_back(rotation, image_width, image_height,
glyph_width, glyph_height,
&src_x, &src_y, &crop_width, &crop_height);
drmmode_crtc->cursor_src_x = src_x;
drmmode_crtc->cursor_src_y = src_y;
@@ -2109,8 +2188,8 @@ drmmode_load_cursor_argb_check(xf86CrtcPtr crtc, CARD32 *image)
/* cursor should be mapped already */
drmmode_paint_cursor(drmmode_cursor.bo, cursor_pitch, cursor_width, cursor_height,
image, image_width, image_height,
drmmode_crtc, glyph_width, glyph_height,
crtc->rotation, src_x, src_y);
drmmode_crtc, crop_width, crop_height,
rotation, src_x, src_y);
/* set cursor width and height here for drmmode_show_cursor */
drmmode_crtc->cursor_width = cursor_width;