Backends: OSX: Fix keyboard support. Handle scroll cancel. Don't set mouse cursor shape unconditionally. (#4759, #4253, #1873)

Note the original FIXME: refered to GLFWs Cocoa implementation, which is largely what this commit provides.

Author: stuartcarnie

backends/imgui_impl_osx.h

@@ -6,10 +6,9 @@
 //  [X] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'.
 //  [X] Platform: OSX clipboard is supported within core Dear ImGui (no specific code in this backend).
 //  [X] Platform: Gamepad support. Enabled with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
-// Issues:
-//  [ ] Platform: Keys are all generally very broken. Best using [event keycode] and not [event characters]..
+//  [X] Platform: Keyboard arrays indexed using kVK_* codes, e.g. ImGui::IsKeyPressed(kVK_Space).
 
-// You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this. 
+// You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
 // If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
 // Read online: https://github.com/ocornut/imgui/tree/master/docs
@@ -19,7 +18,7 @@
 @class NSEvent;
 @class NSView;
 
-IMGUI_IMPL_API bool     ImGui_ImplOSX_Init();
+IMGUI_IMPL_API bool     ImGui_ImplOSX_Init(NSView* _Nonnull view);
 IMGUI_IMPL_API void     ImGui_ImplOSX_Shutdown();
 IMGUI_IMPL_API void     ImGui_ImplOSX_NewFrame(NSView* _Nullable view);
 IMGUI_IMPL_API bool     ImGui_ImplOSX_HandleEvent(NSEvent* _Nonnull event, NSView* _Nullable view);