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Fix touch coordinate transformation for screen rotation #773

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Fix touch coordinate transformation for screen rotation #773

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53 changes: 49 additions & 4 deletions platform/drm/cog-platform-drm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -188,6 +188,7 @@ static struct {
struct udev *udev;
struct libinput *libinput;

CogGLRendererRotation rotation; // 0, 90, 180, 270
uint32_t input_width;
uint32_t input_height;

Expand All @@ -199,6 +200,7 @@ static struct {
} input_data = {
.udev = NULL,
.libinput = NULL,
.rotation = COG_GL_RENDERER_ROTATION_0,
.input_width = 0,
.input_height = 0,
.repeating_key = {0, 0},
Expand Down Expand Up @@ -840,10 +842,51 @@ input_handle_touch_event (enum libinput_event_type touch_type, struct libinput_e

if (touch_type == LIBINPUT_EVENT_TOUCH_DOWN
|| touch_type == LIBINPUT_EVENT_TOUCH_MOTION) {
touch_point->x = libinput_event_touch_get_x_transformed (touch_event,
input_data.input_width);
touch_point->y = libinput_event_touch_get_y_transformed (touch_event,
input_data.input_height);
// Determine transformation parameters based on rotation state
// For 90° and 270° rotations, we need to swap width and height
const int transform_width = (input_data.rotation == COG_GL_RENDERER_ROTATION_90 ||
input_data.rotation == COG_GL_RENDERER_ROTATION_270)
? input_data.input_height : input_data.input_width;

const int transform_height = (input_data.rotation == COG_GL_RENDERER_ROTATION_90 ||
input_data.rotation == COG_GL_RENDERER_ROTATION_270)
? input_data.input_width : input_data.input_height;

// Get raw touch coordinates from libinput event
// These are already normalized to [0, transform_width/height] range
double raw_x = libinput_event_touch_get_x_transformed(touch_event, transform_width);
double raw_y = libinput_event_touch_get_y_transformed(touch_event, transform_height);

// Apply rotation transformation to convert raw coordinates to display coordinates
switch (input_data.rotation) {
case COG_GL_RENDERER_ROTATION_90: // 90° clockwise rotation
// x' = height - y
// y' = x
touch_point->x = transform_height - raw_y;
touch_point->y = raw_x;
break;

case COG_GL_RENDERER_ROTATION_180: // 180° rotation
// x' = width - x
// y' = height - y
touch_point->x = transform_width - raw_x;
touch_point->y = transform_height - raw_y;
break;

case COG_GL_RENDERER_ROTATION_270: // 270° clockwise rotation (90° counter-clockwise)
// x' = y
// y' = width - x
touch_point->x = raw_y;
touch_point->y = transform_width - raw_x;
break;

case COG_GL_RENDERER_ROTATION_0: // No rotation
default:
// Pass through coordinates unchanged
touch_point->x = raw_x;
touch_point->y = raw_y;
break;
}
}
}

Expand Down Expand Up @@ -1247,6 +1290,8 @@ init_input(CogDrmPlatform *platform)
if (!input_data.libinput)
return FALSE;

input_data.rotation = platform->rotation;

int ret = libinput_udev_assign_seat (input_data.libinput, "seat0");
if (ret)
return FALSE;
Expand Down