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render: fixes to how we convert touch events for logical scaling. 

We now handle HiDPI correctly, and touches are clamped to the viewport. So
if you are rendering to a logical 640x480 in a 720p window, and touch the
letterboxing at point (640,700), it will report the touch at (0.5,1.0) instead
of outside the documented range.
This commit is contained in:
Ryan C. Gordon 2020-08-09 00:55:39 -04:00
parent c437729b21
commit a720d1a294
1 changed files with 41 additions and 21 deletions
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52
src/render/SDL_render.c
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@ -693,35 +693,55 @@ SDL_RendererEventWatch(void *userdata, SDL_Event *event)
event->type == SDL_FINGERUP ||
event->type == SDL_FINGERMOTION) {
int logical_w, logical_h;
float physical_w, physical_h;
SDL_Rect viewport;
SDL_FPoint scale;
GetWindowViewportValues(renderer, &logical_w, &logical_h, &viewport, &scale);
if (logical_w) {
int w, h;
/* !!! FIXME: we probably should drop events that are outside of the
!!! FIXME: viewport, but we can't do that from an event watcher,
!!! FIXME: and we would have to track if a touch happened outside
!!! FIXME: the viewport and then slid into it to insert extra
!!! FIXME: events, which is a mess, so for now we just clamp these
!!! FIXME: events to the edge. */
if (renderer->GetOutputSize) {
int w, h;
renderer->GetOutputSize(renderer, &w, &h);
physical_w = (float) w;
physical_h = (float) h;
} else {
int w, h;
SDL_GetWindowSize(renderer->window, &w, &h);
physical_w = ((float) w) * renderer->dpi_scale.x;
physical_h = ((float) h) * renderer->dpi_scale.y;
}
event->tfinger.x *= (w - 1);
event->tfinger.y *= (h - 1);
event->tfinger.x -= (viewport.x * renderer->dpi_scale.x);
event->tfinger.y -= (viewport.y * renderer->dpi_scale.y);
event->tfinger.x = (event->tfinger.x / (scale.x * renderer->dpi_scale.x));
event->tfinger.y = (event->tfinger.y / (scale.y * renderer->dpi_scale.y));
if (logical_w > 1) {
event->tfinger.x = event->tfinger.x / (logical_w - 1);
} else {
if (physical_w == 0.0f) { /* nowhere for the touch to go, avoid division by zero and put it dead center. */
event->tfinger.x = 0.5f;
}
if (logical_h > 1) {
event->tfinger.y = event->tfinger.y / (logical_h - 1);
} else {
const float normalized_viewport_x = ((float) viewport.x) / physical_w;
const float normalized_viewport_w = ((float) viewport.w) / physical_w;
if (event->tfinger.x <= normalized_viewport_x) {
event->tfinger.x = 0.0f; /* to the left of the viewport, clamp to the edge. */
} else if (event->tfinger.x >= (normalized_viewport_x + normalized_viewport_w)) {
event->tfinger.x = 1.0f; /* to the right of the viewport, clamp to the edge. */
} else {
event->tfinger.x = (event->tfinger.x - normalized_viewport_x) / normalized_viewport_w;
}
}
if (physical_h == 0.0f) { /* nowhere for the touch to go, avoid division by zero and put it dead center. */
event->tfinger.y = 0.5f;
} else {
const float normalized_viewport_y = ((float) viewport.y) / physical_h;
const float normalized_viewport_h = ((float) viewport.h) / physical_h;
if (event->tfinger.y <= normalized_viewport_y) {
event->tfinger.y = 0.0f; /* to the left of the viewport, clamp to the edge. */
} else if (event->tfinger.y >= (normalized_viewport_y + normalized_viewport_h)) {
event->tfinger.y = 1.0f; /* to the right of the viewport, clamp to the edge. */
} else {
event->tfinger.y = (event->tfinger.y - normalized_viewport_y) / normalized_viewport_h;
}
}
}