Use 16 bit indices on phones that dont support 32, fixes #19797

drivers/gles2/rasterizer_canvas_gles2.cpp

@@ -317,9 +317,17 @@ void RasterizerCanvasGLES2::_draw_polygon(const int *p_indices, int p_index_coun
 	}
 
 	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, data.polygon_index_buffer);
-	glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, 0, sizeof(int) * p_index_count, p_indices);
-
-	glDrawElements(GL_TRIANGLES, p_index_count, GL_UNSIGNED_INT, 0);
+	if (storage->config.support_32_bits_indices) { //should check for
+		glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, 0, sizeof(int) * p_index_count, p_indices);
+		glDrawElements(GL_TRIANGLES, p_index_count, GL_UNSIGNED_INT, 0);
+	} else {
+		uint16_t *index16 = (uint16_t *)alloca(sizeof(uint16_t) * p_index_count);
+		for (int i = 0; i < p_index_count; i++) {
+			index16[i] = uint16_t(p_indices[i]);
+		}
+		glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, 0, sizeof(uint16_t) * p_index_count, index16);
+		glDrawElements(GL_TRIANGLES, p_index_count, GL_UNSIGNED_SHORT, 0);
+	}
 
 	glBindBuffer(GL_ARRAY_BUFFER, 0);
 	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

drivers/gles2/rasterizer_storage_gles2.cpp

@@ -4658,6 +4658,13 @@ void RasterizerStorageGLES2::initialize() {
 #else
 	config.use_rgba_2d_shadows = !(config.float_texture_supported && config.extensions.has("GL_EXT_texture_rg"));
 #endif
+
+#ifdef GLES_OVER_GL
+	config.support_32_bits_indices = true;
+#else
+	config.support_32_bits_indices = config.extensions.has("GL_OES_element_index_uint");
+#endif
+
 	frame.count = 0;
 	frame.delta = 0;
 	frame.current_rt = NULL;

drivers/gles2/rasterizer_storage_gles2.h

@@ -78,6 +78,8 @@ public:
 		bool force_vertex_shading;
 
 		bool use_rgba_2d_shadows;
+
+		bool support_32_bits_indices;
 	} config;
 
 	struct Resources {