GLFW backend only AddMouseSourceEvent() on Win32

[ypujante]

Version/Branch of Dear ImGui:

Version 1.91.8, Branch: master (master/docking/etc.)

Back-ends:

imgui_impl_glfw.cpp

Compiler, OS:

Emscripten

Details:

This is a follow up to the now closed issue #8373 (see this post)

The backend is not calling AddMouseSourceEvent(ImGuiMouseSource_TouchScreen) so the touch is identified as emitted by a Mouse. Because of how touch have a tendency to instantly teleport to new locations at the time of touch, we need this identification to handle AllowOverlap behaviors.

[ocornut]

As far as I know GLFW doesn't provide that information, so it would need to be added to it somehow (for Linux, OSX, Emscripten etc.). Any form of workaround/PR would be welcome.

We only have a Win32-specific piece of code using raw Win32 data to extract this information.

[ypujante]

I don't mind taking a look at it for emscripten-glfw...

Could you explain how I would reproduce the problem to know when/if I fix it?

[ocornut]

I don't mind taking a look at it for emscripten-glfw...

It would be better if added to GLFW api.

Could you explain how I would reproduce the problem to know when/if I fix it?

From Changelog:

• IO: Added io.AddMouseSourceEvent() and ImGuiMouseSource enum. This is to allow backend to
  specify actual event source between Mouse/TouchScreen/Pen. (Problems with tabs in touch screen #2702, TouchExtraPadding works fine but there's no way to distinguish between mouse and touch input #2334, Any Stylus/Pen user? Looking for feedback to design storage/api for their inputs.. #2372, Support for Windows Pointer Events? #3453, Trying to add touchscreen support to SDL version on a raspberry pi #5693)

And see this comment:

• Problems with tabs in touch screen #2702 (comment)

As e.g. TabItem() uses ImGuiButtonFlags_AllowItemOverlap when a MousePos + MouseDown happens simultaneously with a touch screen, the tab won't be clicked/selected. Calling io.AddMouseSourceEvent(ImGuiMouseSource_TouchScreen); automatically trickle this event sequence over two updates.