WIP fix for 6096
diff --git a/backends/imgui_impl_glfw.cpp b/backends/imgui_impl_glfw.cpp
index 9192d19..e59ae79 100644
--- a/backends/imgui_impl_glfw.cpp
+++ b/backends/imgui_impl_glfw.cpp
@@ -76,6 +76,12 @@
#include <GLFW/glfw3native.h> // for glfwGetWin32Window
#endif
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+#include <emscripten/html5.h>
+//#include "imgui_internal.h" // IMGUI_DEBUG_LOG()
+#endif
+
// We gather version tests as define in order to easily see which features are version-dependent.
#define GLFW_VERSION_COMBINED (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 + GLFW_VERSION_REVISION)
#ifdef GLFW_RESIZE_NESW_CURSOR // Let's be nice to people who pulled GLFW between 2019-04-16 (3.4 define) and 2019-11-29 (cursors defines) // FIXME: Remove when GLFW 3.4 is released?
@@ -285,7 +291,9 @@
bd->PrevUserCallbackScroll(window, xoffset, yoffset);
#ifdef __EMSCRIPTEN__
- xoffset /= 100.0;
+ // Ignore GLFW events: will be process by Emscripten's specific ImGui_ImplEmscripten_WheelCallback().
+ //IMGUI_DEBUG_LOG("[GLFW] dx: %g, dy: %g\n", xoffset, yoffset);
+ return;
#endif
ImGuiIO& io = ImGui::GetIO();
@@ -406,6 +414,27 @@
// Unused in 'master' branch but 'docking' branch will use this, so we declare it ahead of it so if you have to install callbacks you can install this one too.
}
+#ifdef __EMSCRIPTEN__
+static EM_BOOL ImGui_ImplEmscripten_WheelCallback(int, const EmscriptenWheelEvent* ev, void*)
+{
+ // Mimic Emscripten_HandleWheel() in SDL.
+ // Corresponding equivalent in GLFW JS emulation layer has incorrect quantizing preventing small values. See #6096
+ float multiplier = 0.0f;
+ switch (ev->deltaMode)
+ {
+ case DOM_DELTA_PIXEL: multiplier = 1.0f / 100.0f; break; // 100 pixels make up a step.
+ case DOM_DELTA_LINE: multiplier = 1.0f / 3.0f; break; // 3 lines make up a step.
+ case DOM_DELTA_PAGE: multiplier = 80.0f; break; // A page makes up 80 steps.
+ }
+ float wheel_x = ev->deltaX * -multiplier;
+ float wheel_y = ev->deltaY * -multiplier;
+ //IMGUI_DEBUG_LOG("[Em] mode %d dx: %.2f, dy: %.2f, dz: %.2f --> feed %.2f %.2f\n", (int)ev->deltaMode, ev->deltaX, ev->deltaY, ev->deltaZ, wheel_x, wheel_y);
+ ImGuiIO& io = ImGui::GetIO();
+ io.AddMouseWheelEvent(wheel_x, wheel_y);
+ return EM_TRUE;
+}
+#endif
+
void ImGui_ImplGlfw_InstallCallbacks(GLFWwindow* window)
{
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
@@ -503,6 +532,13 @@
if (install_callbacks)
ImGui_ImplGlfw_InstallCallbacks(window);
+ // Register Emscripten Wheel callback to workaround issue in Emscripten GLFW Emulation (#6096)
+ // We intentionally do not check 'if (install_callbacks)' here, as some users may set it to false and call GLFW callback themselves.
+ // FIXME: May break chaining in case user registered their own Emscripten callback?
+#ifdef __EMSCRIPTEN__
+ emscripten_set_wheel_callback(EMSCRIPTEN_EVENT_TARGET_DOCUMENT, NULL, false, ImGui_ImplEmscripten_WheelCallback);
+#endif
+
bd->ClientApi = client_api;
return true;
}
