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Backends: GLFW: Registering custom low-level mouse wheel handler to get more accurate scrolling impulses on Emscripten. (#4019, #6096)

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Namely, GLFW JS emulation seems to quantize values to a min of -1/+1 which breaks modern OSX/Windows emulating smoothness with stepping wheels (slow steps are sending sub-1.0 values)
+ Massage changelog.
This commit is contained in:
ocornut
2023-02-03 15:00:41 +01:00
parent 6584de4a78
commit d0b1aaa076
2 changed files with 46 additions and 19 deletions
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35
backends/imgui_impl_glfw.cpp
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@ -16,7 +16,7 @@
// CHANGELOG
// (minor and older changes stripped away, please see git history for details)
// 2023-02-02: Inputs: Scaling X value on Emscripten (bug?). (#4019, #6096)
// 2023-02-03: Emscripten: Registering custom low-level mouse wheel handler to get more accurate scrolling impulses on Emscripten. (#4019, #6096)
// 2023-01-04: Inputs: Fixed mods state on Linux when using Alt-GR text input (e.g. German keyboard layout), could lead to broken text input. Revert a 2022/01/17 change were we resumed using mods provided by GLFW, turns out they were faulty.
// 2022-11-22: Perform a dummy glfwGetError() read to cancel missing names with glfwGetKeyName(). (#5908)
// 2022-10-18: Perform a dummy glfwGetError() read to cancel missing mouse cursors errors. Using GLFW_VERSION_COMBINED directly. (#5785)
@ -76,6 +76,11 @@
#include <GLFW/glfw3native.h> // for glfwGetWin32Window
#endif
#ifdef __EMSCRIPTEN__
#include <emscripten.h>
#include <emscripten/html5.h>
#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 +290,8 @@ void ImGui_ImplGlfw_ScrollCallback(GLFWwindow* window, double xoffset, double yo
bd->PrevUserCallbackScroll(window, xoffset, yoffset);
#ifdef __EMSCRIPTEN__
xoffset /= 100.0;
// Ignore GLFW events: will be processed in ImGui_ImplEmscripten_WheelCallback().
return;
#endif
ImGuiIO& io = ImGui::GetIO();
@ -406,6 +412,24 @@ void ImGui_ImplGlfw_MonitorCallback(GLFWmonitor*, int)
// 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;
if (ev->deltaMode == DOM_DELTA_PIXEL) { multiplier = 1.0f / 100.0f; } // 100 pixels make up a step.
else if (ev->deltaMode == DOM_DELTA_LINE) { multiplier = 1.0f / 3.0f; } // 3 lines make up a step.
else if (ev->deltaMode == DOM_DELTA_PAGE) { multiplier = 80.0f; } // A page makes up 80 steps.
float wheel_x = ev->deltaX * -multiplier;
float wheel_y = ev->deltaY * -multiplier;
ImGuiIO& io = ImGui::GetIO();
io.AddMouseWheelEvent(wheel_x, wheel_y);
//IMGUI_DEBUG_LOG("[Emsc] 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);
return EM_TRUE;
}
#endif
void ImGui_ImplGlfw_InstallCallbacks(GLFWwindow* window)
{
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
@ -503,6 +527,13 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
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;
}