Wayland: Issue with mouse wheel coordinates

Apply the fix suggested by @shurizzle in #669, requiring SDL 2.26+.

This does not apply on macOS because the wheel events are dispatched
by custom event handling code (due to trackpad swipe handling) and
therefore don't have the mouse coordinates included.

IssueID #612
IssueID #669

src/app.c

@@ -169,6 +169,7 @@ struct Impl_App {
     uint32_t     elapsedSinceLastTicker;
     iBool        isRunning;
     iBool        isRunningUnderWindowSystem;
+    iBool        isRunningUnderWayland;
     iBool        isTextInputActive;
     iBool        isDarkSystemTheme;
     iBool        isSuspended;
@@ -1153,9 +1154,11 @@ static void init_App_(iApp *d, int argc, char **argv) {
     migrateInternalUserDirToExternalStorage_App_(d);
 #endif
 #if defined (iPlatformLinux) && !defined (iPlatformAndroid) && !defined (iPlatformTerminal)
-    d->isRunningUnderWindowSystem = !iCmpStr(SDL_GetCurrentVideoDriver(), "x11") ||
-                                    !iCmpStr(SDL_GetCurrentVideoDriver(), "wayland");
+    d->isRunningUnderWayland      = !iCmpStr(SDL_GetCurrentVideoDriver(), "wayland");
+    d->isRunningUnderWindowSystem = d->isRunningUnderWayland ||
+                                    !iCmpStr(SDL_GetCurrentVideoDriver(), "x11");
 #else
+    d->isRunningUnderWayland      = iFalse;
     d->isRunningUnderWindowSystem = iTrue;
 #endif
     d->isTextInputActive = iFalse;
@@ -3011,6 +3014,10 @@ iBool isRunningUnderWindowSystem_App(void) {
     return app_.isRunningUnderWindowSystem;
 }
 
+iBool isRunningUnderWayland_App(void) {
+    return app_.isRunningUnderWayland;
+}
+
 void setTextInputActive_App(iBool active) {
     app_.isTextInputActive = active;
     if (active) {

src/app.h

@@ -92,6 +92,7 @@ void                refresh_App                 (void);
 
 iBool               isFinishedLaunching_App     (void);
 iBool               isRunningUnderWindowSystem_App(void);
+iBool               isRunningUnderWayland_App   (void);
 iBool               isRefreshPending_App        (void);
 iBool               isLandscape_App             (void);
 iLocalDef iBool     isPortrait_App              (void) { return !isLandscape_App(); }

src/ui/util.c

@@ -61,6 +61,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
 #include <the_Foundation/math.h>
 #include <the_Foundation/path.h>
 #include <SDL_timer.h>
+#include <SDL_version.h>
 
 iBool isCommand_SDLEvent(const SDL_Event *d) {
     return d->type == SDL_USEREVENT && d->user.code == command_UserEventCode;
@@ -106,13 +107,17 @@ iInt2 coord_MouseWheelEvent(const SDL_MouseWheelEvent *ev) {
     iWindow *win = get_Window(); /* may not be the focus window */
 #if !defined (iPlatformTerminal)
     if (isDesktop_Platform()) {
+# if SDL_VERSION_ATLEAST(2, 26, 0) && !defined(iPlatformApple)
+        return coord_Window(win, ev->mouseX, ev->mouseY);
+# else
         /* We need to figure out where the mouse is in relation to the currently active window.
            It may be outside the actual focus window. */
         iInt2 mousePos, winPos;
         SDL_GetGlobalMouseState(&mousePos.x, &mousePos.y);
         SDL_GetWindowPosition(win->win, &winPos.x, &winPos.y);
         subv_I2(&mousePos, winPos);
         return coord_Window(win, mousePos.x, mousePos.y);
+# endif
     }
 #endif
     return mouseCoord_Window(win, ev->which);