Hackfix some cases the IME on windows locks up

Asking the IME to cancel when the canvas takes focus fixes the case where:

- Windows input lang set to Chinese
- Input mode set to english instead of chinese
- You spam the M key while launching a sch/pcb from the kicad.exe until the editor opens
- The windows would then normally be frozen

common/draw_panel_gal.cpp

@@ -186,6 +186,7 @@ EDA_DRAW_PANEL_GAL::~EDA_DRAW_PANEL_GAL()
 
 void EDA_DRAW_PANEL_GAL::SetFocus()
 {
+    KIPLATFORM::UI::ImeNotifyCancelComposition( this );
     wxScrolledCanvas::SetFocus();
     m_lostFocus = false;
 }

libs/kiplatform/gtk/ui.cpp

@@ -321,6 +321,11 @@ void KIPLATFORM::UI::ImmControl( wxWindow* aWindow, bool aEnable )
 }
 
 
+void KIPLATFORM::UI::ImeNotifyCancelComposition( wxWindow* aWindow )
+{
+}
+
+
 void KIPLATFORM::UI::SetFloatLevel( wxWindow* aWindow )
 {
 }

libs/kiplatform/include/kiplatform/ui.h

@@ -158,6 +158,11 @@ namespace KIPLATFORM
          */
         void ImmControl( wxWindow* aWindow, bool aEnable );
 
+        /**
+         * Asks the IME to cancel
+         */
+        void ImeNotifyCancelComposition( wxWindow* aWindow );
+
         /**
          * On Wayland, restricts the pointer movement to a rectangle slightly bigger than the given `wxWindow`.
          * This way, the cursor doesn't exit the (bigger) application window and we retain control on it.

libs/kiplatform/msw/ui.cpp

@@ -184,6 +184,14 @@ void KIPLATFORM::UI::ImmControl( wxWindow* aWindow, bool aEnable )
 }
 
 
+void KIPLATFORM::UI::ImeNotifyCancelComposition( wxWindow* aWindow )
+{
+    const HIMC himc = ImmGetContext( aWindow->GetHWND() );
+    ImmNotifyIME( himc, NI_COMPOSITIONSTR, CPS_CANCEL, 0 );
+    ImmReleaseContext( aWindow->GetHWND(), himc );
+}
+
+
 bool KIPLATFORM::UI::InfiniteDragPrepareWindow( wxWindow* aWindow )
 {
     return true;

libs/kiplatform/osx/ui.mm

@@ -184,6 +184,11 @@ void KIPLATFORM::UI::ImmControl( wxWindow* aWindow, bool aEnable )
 }
 
 
+void KIPLATFORM::UI::ImeNotifyCancelComposition( wxWindow* aWindow )
+{
+}
+
+
 bool KIPLATFORM::UI::InfiniteDragPrepareWindow( wxWindow* aWindow )
 {
     return true;