From 45bb7f6ef4bcd660e282c2f61cde0afa095236b6 Mon Sep 17 00:00:00 2001
From: Frank Praznik <[EMAIL REDACTED]>
Date: Wed, 16 Sep 2026 22:56:13 -0400
Subject: [PATCH] Scale mouse coordinates only when the main view has a logical
presentation mode set
When a render target is bound, querying the logical presentation mode will report the presentation mode on the render target, which can differ from the mode set on the main view. When a render target is bound, store the main view logical presentation mode and use it to determine whether mouse coordinates in events should be implicitly scaled, as the main view is always used to transform event coordinates.
---
src/sdl2_compat.c | 77 ++++++++++++++++++++++++++++++++++++-----------
1 file changed, 60 insertions(+), 17 deletions(-)
diff --git a/src/sdl2_compat.c b/src/sdl2_compat.c
index 77723e55..2ecc7772 100644
--- a/src/sdl2_compat.c
+++ b/src/sdl2_compat.c
@@ -217,6 +217,7 @@ do { \
#define PROP_RENDERER_BATCHING "sdl2-compat.renderer.batching"
#define PROP_RENDERER_RELATIVE_SCALING "sdl2-compat.renderer.relative-scaling"
#define PROP_RENDERER_INTEGER_SCALE "sdl2-compat.renderer.integer_scale"
+#define PROP_RENDERER_MAIN_VIEW_LOGICAL_PRESENTATION "sdl2-compat.renderer.main_view_logical_presentation"
#define PROP_TEXTURE_SCALE_MODE "sdl2-compat.texture.scale_mode"
#define PROP_SURFACE2 "sdl2-compat.surface2"
#define PROP_STREAM2 "sdl2-compat.stream2"
@@ -2280,6 +2281,24 @@ static SDL_AudioDeviceID AudioDeviceID3to2(SDL_AudioDeviceID id)
static int GetIndexFromJoystickInstance(SDL_JoystickID jid);
+static bool ShouldTransformMouseCoordinates(SDL_Renderer *renderer)
+{
+ /* The mouse coordinates should only be transformed if the main view is using a
+ * logical presentation mode, as it can differ from the mode set on a render target.
+ */
+ SDL_RendererLogicalPresentation mode = SDL_LOGICAL_PRESENTATION_DISABLED;
+ const int propval = (int)SDL3_GetNumberProperty(SDL3_GetRendererProperties(renderer),
+ PROP_RENDERER_MAIN_VIEW_LOGICAL_PRESENTATION, -1);
+ if (propval == -1) {
+ /* No render target bound, query the presentation mode directly. */
+ SDL3_GetRenderLogicalPresentation(renderer, NULL, NULL, &mode);
+ } else {
+ mode = (SDL_RendererLogicalPresentation)propval;
+ }
+
+ return mode != SDL_LOGICAL_PRESENTATION_DISABLED;
+}
+
static SDL2_Event *Event3to2(const SDL_Event *event3, SDL2_Event *event2)
{
SDL_Renderer *renderer;
@@ -2336,18 +2355,20 @@ static SDL2_Event *Event3to2(const SDL_Event *event3, SDL2_Event *event2)
case SDL_EVENT_MOUSE_MOTION:
renderer = SDL3_GetRenderer(SDL3_GetWindowFromID(event3->motion.windowID));
if (renderer) {
- SDL3_memcpy(&cvtevent3, event3, sizeof (SDL_Event));
- SDL3_ConvertEventToRenderCoordinates(renderer, &cvtevent3);
- if (SDL3_GetBooleanProperty(SDL3_GetRendererProperties(renderer), PROP_RENDERER_RELATIVE_SCALING, true)) {
- /* Accumulate scaled relative motion */
- residual_motion_x = SDL3_modff(residual_motion_x + cvtevent3.motion.xrel, &cvtevent3.motion.xrel);
- residual_motion_y = SDL3_modff(residual_motion_y + cvtevent3.motion.yrel, &cvtevent3.motion.yrel);
- } else {
- /* Undo the relative scaling that SDL_ConvertEventToRenderCoordinates() performed */
- cvtevent3.motion.xrel = event3->motion.xrel;
- cvtevent3.motion.yrel = event3->motion.yrel;
+ if (ShouldTransformMouseCoordinates(renderer)) {
+ SDL3_memcpy(&cvtevent3, event3, sizeof (SDL_Event));
+ SDL3_ConvertEventToRenderCoordinates(renderer, &cvtevent3);
+ if (SDL3_GetBooleanProperty(SDL3_GetRendererProperties(renderer), PROP_RENDERER_RELATIVE_SCALING, true)) {
+ /* Accumulate scaled relative motion */
+ residual_motion_x = SDL3_modff(residual_motion_x + cvtevent3.motion.xrel, &cvtevent3.motion.xrel);
+ residual_motion_y = SDL3_modff(residual_motion_y + cvtevent3.motion.yrel, &cvtevent3.motion.yrel);
+ } else {
+ /* Undo the relative scaling that SDL_ConvertEventToRenderCoordinates() performed */
+ cvtevent3.motion.xrel = event3->motion.xrel;
+ cvtevent3.motion.yrel = event3->motion.yrel;
+ }
+ event3 = &cvtevent3;
}
- event3 = &cvtevent3;
}
if (UseSDL2PrereleaseEvents) {
SDL2PRERELEASE_MouseMotionEvent *motion = (SDL2PRERELEASE_MouseMotionEvent *)&event2->motion;
@@ -2368,9 +2389,11 @@ static SDL2_Event *Event3to2(const SDL_Event *event3, SDL2_Event *event2)
case SDL_EVENT_MOUSE_BUTTON_UP:
renderer = SDL3_GetRenderer(SDL3_GetWindowFromID(event3->button.windowID));
if (renderer) {
- SDL3_memcpy(&cvtevent3, event3, sizeof(SDL_Event));
- SDL3_ConvertEventToRenderCoordinates(renderer, &cvtevent3);
- event3 = &cvtevent3;
+ if (ShouldTransformMouseCoordinates(renderer)) {
+ SDL3_memcpy(&cvtevent3, event3, sizeof (SDL_Event));
+ SDL3_ConvertEventToRenderCoordinates(renderer, &cvtevent3);
+ event3 = &cvtevent3;
+ }
}
if (UseSDL2PrereleaseEvents) {
SDL2PRERELEASE_MouseButtonEvent *button = (SDL2PRERELEASE_MouseButtonEvent *)&event2->button;
@@ -2387,9 +2410,11 @@ static SDL2_Event *Event3to2(const SDL_Event *event3, SDL2_Event *event2)
case SDL_EVENT_MOUSE_WHEEL:
renderer = SDL3_GetRenderer(SDL3_GetWindowFromID(event3->wheel.windowID));
if (renderer) {
- SDL3_memcpy(&cvtevent3, event3, sizeof(SDL_Event));
- SDL3_ConvertEventToRenderCoordinates(renderer, &cvtevent3);
- event3 = &cvtevent3;
+ if (ShouldTransformMouseCoordinates(renderer)) {
+ SDL3_memcpy(&cvtevent3, event3, sizeof (SDL_Event));
+ SDL3_ConvertEventToRenderCoordinates(renderer, &cvtevent3);
+ event3 = &cvtevent3;
+ }
}
if (UseSDL2PrereleaseEvents) {
SDL2PRERELEASE_MouseWheelEvent *wheel = (SDL2PRERELEASE_MouseWheelEvent *)&event2->wheel;
@@ -6181,6 +6206,24 @@ SDL_RenderSetClipRect(SDL_Renderer *renderer, const SDL_Rect *rect)
SDL_DECLSPEC int SDLCALL
SDL_SetRenderTarget(SDL_Renderer *renderer, SDL_Texture *texture)
{
+ if (!renderer) {
+ return -1;
+ }
+
+ if (texture) {
+ /* When initially setting a render target, store the main view logical presentation mode,
+ * as it needs to be queried when potentially transforming mouse coordinates in events.
+ */
+ SDL_Texture *current_target = SDL3_GetRenderTarget(renderer);
+ if (!current_target) {
+ SDL_RendererLogicalPresentation mode = SDL_LOGICAL_PRESENTATION_DISABLED;
+ SDL3_GetRenderLogicalPresentation(renderer, NULL, NULL, &mode);
+ SDL3_SetNumberProperty(SDL3_GetRendererProperties(renderer), PROP_RENDERER_MAIN_VIEW_LOGICAL_PRESENTATION, mode);
+ }
+ } else {
+ SDL3_ClearProperty(SDL3_GetRendererProperties(renderer), PROP_RENDERER_MAIN_VIEW_LOGICAL_PRESENTATION);
+ }
+
if (!SDL3_SetRenderTarget(renderer, texture)) {
return -1;
}