Add test for findCanvasEventTarget's various cases

Author: JoeOsborn

src/library_html5.js

@@ -363,7 +363,7 @@ var LibraryHTML5 = {
     // If not found, if one is querying by using DOM tag name selector 'canvas', grab the first
     // OffscreenCanvas that we can find.
      || (target == 'canvas' && Object.values(GL.offscreenCanvases)[0])
-    // If that is not found either, query via the regular DOM selector.
+    // If that is not found either, query via the regular findEventTarget mechanism.
      || findEventTarget(target);
   },
 #else

test/browser/html5_special_canvas_event_targets.cpp

@@ -0,0 +1,36 @@
+// Copyright 2024 The Emscripten Authors.  All rights reserved.
+// Emscripten is available under two separate licenses, the MIT license and the
+// University of Illinois/NCSA Open Source License.  Both these licenses can be
+// found in the LICENSE file.
+
+#include <GLES2/gl2.h>
+#include <GLES2/gl2ext.h>
+#include <assert.h>
+
+#include <emscripten/emscripten.h>
+#include <emscripten/html5.h>
+
+const char *TARGETS[]={"!foovas", "#canvas", "canvas"};
+const char *target = TARGETS[WHICH_TARGET];
+
+int main()
+{
+  EM_ASM({
+    specialHTMLTargets["!foovas"] = Module.canvas;
+  });
+  int w=0, h=0;
+  EMSCRIPTEN_RESULT res = emscripten_get_canvas_element_size(target, &w, &h);
+  assert(res == EMSCRIPTEN_RESULT_SUCCESS);
+  EmscriptenWebGLContextAttributes attrs;
+  emscripten_webgl_init_context_attributes(&attrs);
+  EMSCRIPTEN_WEBGL_CONTEXT_HANDLE context = emscripten_webgl_create_context(target, &attrs);
+  assert(context > 0);
+  res = emscripten_webgl_make_context_current(context);
+  assert(res == EMSCRIPTEN_RESULT_SUCCESS);
+  assert(emscripten_webgl_get_current_context() == context);
+  res = emscripten_get_canvas_element_size(target, &w, &h);
+  assert(res == EMSCRIPTEN_RESULT_SUCCESS);
+  res = emscripten_webgl_destroy_context(context);
+  assert(res == EMSCRIPTEN_RESULT_SUCCESS);
+  return 0;
+}

test/test_browser.py

@@ -2618,6 +2618,18 @@ def test_html5_webgl_create_context2(self):
   def test_html5_special_event_targets(self):
     self.btest_exit('html5_special_event_targets.cpp', args=['-lGL'])
 
+  @parameterized({
+    '': ([],),
+    'offscreen_no_pthread': (['-sOFFSCREENCANVAS_SUPPORT'],),
+    'offscreen_pthread': (['-sOFFSCREENCANVAS_SUPPORT', '-sPROXY_TO_PTHREAD', '-pthread'],),
+  })
+  @requires_graphics_hardware
+  # Verify bug https://github.com/emscripten-core/emscripten/issues/22942: findCanvasEventTarget doesn't use specialHTMLTargets
+  def test_html5_special_canvas_event_targets(self, args):
+    self.btest_exit('html5_special_canvas_event_targets.cpp', args=args + ['-lGL', '-sDISABLE_DEPRECATED_FIND_EVENT_TARGET_BEHAVIOR=1', '-DWHICH_TARGET=0'])
+    self.btest_exit('html5_special_canvas_event_targets.cpp', args=args + ['-lGL', '-sDISABLE_DEPRECATED_FIND_EVENT_TARGET_BEHAVIOR=1', '-DWHICH_TARGET=1'])
+    self.btest_exit('html5_special_canvas_event_targets.cpp', args=args + ['-lGL', '-sDISABLE_DEPRECATED_FIND_EVENT_TARGET_BEHAVIOR=1', '-DWHICH_TARGET=2'])
+
   @requires_graphics_hardware
   def test_html5_webgl_destroy_context(self):
     for opts in ([], ['-O2', '-g1'], ['-sFULL_ES2']):