Added ImGuiKey_MouseXXX aliases. (#4921) Reworked SetItemUsingMouseWheel() to use this for ActiveId. (#2891)

The rework of SetItemUsingMouseWheel() is half-complete since there's a HoveredIdUsingMouseWheel component. This will however be totally cleaned when we transtion to InputOwner system.
diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index f624268..0b665e2 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -56,7 +56,10 @@
 
 - InputText: added experimental io.ConfigInputTextEnterKeepActive feature to make pressing
   Enter keep the input active and select all text.
+- IO: Added ImGuiKey_MouseXXX aliases for mouse buttons/wheel so all operations done on ImGuiKey
+  can apply to mouse data as well. (#4921)
 - Nav: Fixed moving/resizing window with gamepad or keyboard when running at very high framerate.
+- Nav: Pressing Space/GamepadFaceDown on a repeating button uses the same repeating rate as a mouse hold.
 - Misc: io.Framerate moving average now converge in 60 frames instead of 120. (#5236, #4138)
 - Tools: Item Picker: Mouse button can be changed by holding Ctrl+Shift, making it easier
   to use the Item Picker in e.g. menus. (#2673)
diff --git a/imgui.cpp b/imgui.cpp
index 11ecf78..27cee0f 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -1278,6 +1278,7 @@
     ImGuiContext& g = *GImGui;
     IM_ASSERT(&g.IO == this && "Can only add events to current context.");
     IM_ASSERT(ImGui::IsNamedKey(key)); // Backend needs to pass a valid ImGuiKey_ constant. 0..511 values are legacy native key codes which are not accepted by this API.
+    IM_ASSERT(!ImGui::IsAliasKey(key)); // Backend cannot submit ImGuiKey_MouseXXX values they are automatically inferred from AddMouseXXX() events.
 
     // Verify that backend isn't mixing up using new io.AddKeyEvent() api and old io.KeysDown[] + io.KeyMap[] data.
 #ifndef IMGUI_DISABLE_OBSOLETE_KEYIO
@@ -3423,7 +3424,6 @@
 
     // Clear declaration of inputs claimed by the widget
     // (Please note that this is WIP and not all keys/inputs are thoroughly declared by all widgets yet)
-    g.ActiveIdUsingMouseWheel = false;
     g.ActiveIdUsingNavDirMask = 0x00;
     g.ActiveIdUsingKeyInputMask.ClearAllBits();
 #ifndef IMGUI_DISABLE_OBSOLETE_KEYIO
@@ -3961,6 +3961,14 @@
     return (window->Active) && (!window->Hidden);
 }
 
+static void UpdateAliasKey(ImGuiKey key, bool v, float analog_value)
+{
+    IM_ASSERT(ImGui::IsAliasKey(key));
+    ImGuiKeyData* key_data = ImGui::GetKeyData(key);
+    key_data->Down = v;
+    key_data->AnalogValue = analog_value;
+}
+
 static void ImGui::UpdateKeyboardInputs()
 {
     ImGuiContext& g = *GImGui;
@@ -4034,8 +4042,12 @@
 
 #endif
 
-    // Synchronize io.KeyMods with individual modifiers io.KeyXXX bools
+    // Synchronize io.KeyMods with individual modifiers io.KeyXXX bools, update aliases
     io.KeyMods = GetMergedModFlags();
+    for (int n = 0; n < ImGuiMouseButton_COUNT; n++)
+        UpdateAliasKey(MouseButtonToKey(n), io.MouseDown[n], io.MouseDown[n] ? 1.0f : 0.0f);
+    UpdateAliasKey(ImGuiKey_MouseWheelX, io.MouseWheelH != 0.0f, io.MouseWheelH);
+    UpdateAliasKey(ImGuiKey_MouseWheelY, io.MouseWheel != 0.0f, io.MouseWheel);
 
     // Clear gamepad data if disabled
     if ((io.BackendFlags & ImGuiBackendFlags_HasGamepad) == 0)
@@ -4142,12 +4154,13 @@
         }
     }
 
-    float wheel_x = g.IO.MouseWheelH;
-    float wheel_y = g.IO.MouseWheel;
-    if (wheel_x == 0.0f && wheel_y == 0.0f)
-        return;
+    const bool hovered_id_using_mouse_wheel = (g.HoveredIdPreviousFrame != 0 && g.HoveredIdPreviousFrameUsingMouseWheel);
+    const bool active_id_using_mouse_wheel_x = g.ActiveIdUsingKeyInputMask.TestBit(ImGuiKey_MouseWheelX);
+    const bool active_id_using_mouse_wheel_y = g.ActiveIdUsingKeyInputMask.TestBit(ImGuiKey_MouseWheelY);
 
-    if ((g.ActiveId != 0 && g.ActiveIdUsingMouseWheel) || (g.HoveredIdPreviousFrame != 0 && g.HoveredIdPreviousFrameUsingMouseWheel))
+    float wheel_x = (!hovered_id_using_mouse_wheel && !active_id_using_mouse_wheel_x) ? g.IO.MouseWheelH : 0.0f;
+    float wheel_y = (!hovered_id_using_mouse_wheel && !active_id_using_mouse_wheel_y) ? g.IO.MouseWheel : 0;
+    if (wheel_x == 0.0f && wheel_y == 0.0f)
         return;
 
     ImGuiWindow* window = g.WheelingWindow ? g.WheelingWindow : g.HoveredWindow;
@@ -5206,7 +5219,10 @@
     if (g.HoveredId == id)
         g.HoveredIdUsingMouseWheel = true;
     if (g.ActiveId == id)
-        g.ActiveIdUsingMouseWheel = true;
+    {
+        g.ActiveIdUsingKeyInputMask.SetBit(ImGuiKey_MouseWheelX);
+        g.ActiveIdUsingKeyInputMask.SetBit(ImGuiKey_MouseWheelY);
+    }
 }
 
 void ImGui::SetActiveIdUsingNavAndKeys()
@@ -7662,7 +7678,8 @@
     "GamepadL1", "GamepadR1", "GamepadL2", "GamepadR2", "GamepadL3", "GamepadR3",
     "GamepadLStickLeft", "GamepadLStickRight", "GamepadLStickUp", "GamepadLStickDown",
     "GamepadRStickLeft", "GamepadRStickRight", "GamepadRStickUp", "GamepadRStickDown",
-    "ModCtrl", "ModShift", "ModAlt", "ModSuper"
+    "ModCtrl", "ModShift", "ModAlt", "ModSuper",
+    "MouseLeft", "MouseRight", "MouseMiddle", "MouseX1", "MouseX2", "MouseWheelX", "MouseWheelY",
 };
 IM_STATIC_ASSERT(ImGuiKey_NamedKey_COUNT == IM_ARRAYSIZE(GKeyNames));
 
@@ -12691,7 +12708,7 @@
         int active_id_using_key_input_count = 0;
         for (int n = ImGuiKey_NamedKey_BEGIN; n < ImGuiKey_NamedKey_END; n++)
             active_id_using_key_input_count += g.ActiveIdUsingKeyInputMask[n] ? 1 : 0;
-        Text("ActiveIdUsing: Wheel: %d, NavDirMask: %X, KeyInputMask: %d key(s)", g.ActiveIdUsingMouseWheel, g.ActiveIdUsingNavDirMask, active_id_using_key_input_count);
+        Text("ActiveIdUsing: NavDirMask: %X, KeyInputMask: %d key(s)", g.ActiveIdUsingNavDirMask, active_id_using_key_input_count);
         Text("HoveredId: 0x%08X (%.2f sec), AllowOverlap: %d", g.HoveredIdPreviousFrame, g.HoveredIdTimer, g.HoveredIdAllowOverlap); // Not displaying g.HoveredId as it is update mid-frame
         Text("DragDrop: %d, SourceId = 0x%08X, Payload \"%s\" (%d bytes)", g.DragDropActive, g.DragDropPayload.SourceId, g.DragDropPayload.DataType, g.DragDropPayload.DataSize);
         Unindent();
diff --git a/imgui.h b/imgui.h
index d8c7d7d..a239044 100644
--- a/imgui.h
+++ b/imgui.h
@@ -1432,6 +1432,10 @@
     //   backends tend to interfere and break that equivalence. The safer decision is to relay that ambiguity down to the end-user...
     ImGuiKey_ModCtrl, ImGuiKey_ModShift, ImGuiKey_ModAlt, ImGuiKey_ModSuper,
 
+    // Mouse Buttons (auto-submitted from AddMouseButtonEvent() calls)
+    // - This is mirroring the data also written to io.MouseDown[], io.MouseWheel, in a format allowing them to be accessed via standard key API.
+    ImGuiKey_MouseLeft, ImGuiKey_MouseRight, ImGuiKey_MouseMiddle, ImGuiKey_MouseX1, ImGuiKey_MouseX2, ImGuiKey_MouseWheelX, ImGuiKey_MouseWheelY,
+
     // End of list
     ImGuiKey_COUNT,                 // No valid ImGuiKey is ever greater than this value
 
diff --git a/imgui_internal.h b/imgui_internal.h
index 32136cf..0bc686e 100644
--- a/imgui_internal.h
+++ b/imgui_internal.h
@@ -1177,6 +1177,8 @@
     ImGuiKey_LegacyNativeKey_END    = 512,
     ImGuiKey_Gamepad_BEGIN          = ImGuiKey_GamepadStart,
     ImGuiKey_Gamepad_END            = ImGuiKey_GamepadRStickDown + 1,
+    ImGuiKey_Aliases_BEGIN          = ImGuiKey_MouseLeft,
+    ImGuiKey_Aliases_END            = ImGuiKey_COUNT,
 
     // [Internal] Named shortcuts for Navigation
     ImGuiKey_NavKeyboardTweakSlow   = ImGuiKey_ModCtrl,
@@ -1246,11 +1248,9 @@
     // Flags for IsKeyPressedEx()
     ImGuiInputReadFlags_None                = 0,
     ImGuiInputReadFlags_Repeat              = 1 << 0,   // Return true on successive repeats. Default for legacy IsKeyPressed(). NOT Default for legacy IsMouseClicked(). MUST BE == 1.
-
-    // Repeat rate
-    ImGuiInputReadFlags_RepeatRateDefault   = 1 << 1,   // Regular
-    ImGuiInputReadFlags_RepeatRateNavMove   = 1 << 2,   // Fast
-    ImGuiInputReadFlags_RepeatRateNavTweak  = 1 << 3,   // Faster
+    ImGuiInputReadFlags_RepeatRateDefault   = 1 << 1,   // Repeat rate: Regular (default)
+    ImGuiInputReadFlags_RepeatRateNavMove   = 1 << 2,   // Repeat rate: Fast
+    ImGuiInputReadFlags_RepeatRateNavTweak  = 1 << 3,   // Repeat rate: Faster
     ImGuiInputReadFlags_RepeatRateMask_     = ImGuiInputReadFlags_RepeatRateDefault | ImGuiInputReadFlags_RepeatRateNavMove | ImGuiInputReadFlags_RepeatRateNavTweak,
 };
 
@@ -1651,7 +1651,6 @@
     float                   LastActiveIdTimer;                  // Store the last non-zero ActiveId timer since the beginning of activation, useful for animation.
 
     // Input Ownership
-    bool                    ActiveIdUsingMouseWheel;            // Active widget will want to read mouse wheel. Blocks scrolling the underlying window.
     ImU32                   ActiveIdUsingNavDirMask;            // Active widget will want to read those nav move requests (e.g. can activate a button and move away from it)
     ImBitArrayForNamedKeys  ActiveIdUsingKeyInputMask;          // Active widget will want to read those key inputs. When we grow the ImGuiKey enum we'll need to either to order the enum to make useful keys come first, either redesign this into e.g. a small array.
 #ifndef IMGUI_DISABLE_OBSOLETE_KEYIO
@@ -1896,7 +1895,6 @@
         LastActiveId = 0;
         LastActiveIdTimer = 0.0f;
 
-        ActiveIdUsingMouseWheel = false;
         ActiveIdUsingNavDirMask = 0x00;
         ActiveIdUsingKeyInputMask.ClearAllBits();
 #ifndef IMGUI_DISABLE_OBSOLETE_KEYIO
@@ -2700,6 +2698,7 @@
     inline bool             IsNamedKey(ImGuiKey key)                                    { return key >= ImGuiKey_NamedKey_BEGIN && key < ImGuiKey_NamedKey_END; }
     inline bool             IsLegacyKey(ImGuiKey key)                                   { return key >= ImGuiKey_LegacyNativeKey_BEGIN && key < ImGuiKey_LegacyNativeKey_END; }
     inline bool             IsGamepadKey(ImGuiKey key)                                  { return key >= ImGuiKey_Gamepad_BEGIN && key < ImGuiKey_Gamepad_END; }
+    inline bool             IsAliasKey(ImGuiKey key)                                    { return key >= ImGuiKey_Aliases_BEGIN && key < ImGuiKey_Aliases_END; }
     IMGUI_API ImGuiKeyData* GetKeyData(ImGuiKey key);
     IMGUI_API void          GetKeyChordName(ImGuiModFlags mods, ImGuiKey key, char* out_buf, int out_buf_size);
     IMGUI_API void          SetItemUsingMouseWheel();
@@ -2707,6 +2706,7 @@
     inline bool             IsActiveIdUsingNavDir(ImGuiDir dir)                         { ImGuiContext& g = *GImGui; return (g.ActiveIdUsingNavDirMask & (1 << dir)) != 0; }
     inline bool             IsActiveIdUsingKey(ImGuiKey key)                            { ImGuiContext& g = *GImGui; return g.ActiveIdUsingKeyInputMask[key]; }
     inline void             SetActiveIdUsingKey(ImGuiKey key)                           { ImGuiContext& g = *GImGui; g.ActiveIdUsingKeyInputMask.SetBit(key); }
+    inline ImGuiKey         MouseButtonToKey(ImGuiMouseButton button)                   { IM_ASSERT(button >= 0 && button < ImGuiMouseButton_COUNT); return ImGuiKey_MouseLeft + button; }
     IMGUI_API bool          IsMouseDragPastThreshold(ImGuiMouseButton button, float lock_threshold = -1.0f);
     IMGUI_API ImGuiModFlags GetMergedModFlags();
     IMGUI_API ImVec2        GetKeyVector2d(ImGuiKey key_left, ImGuiKey key_right, ImGuiKey key_up, ImGuiKey key_down);