Added ImGuiKeyModFlags. Added additional checks in EndFrame() to verify that io.KeyXXX values have not been tampered with between NewFrame() and EndFrame().

docs/CHANGELOG.txt

@@ -57,6 +57,8 @@ Other Changes:
 - Window: Fixed a bug with child window inheriting ItemFlags from their parent when the child
   window also manipulate the ItemFlags stack. (#3024) [@Stanbroek]
 - Font: Fixed non-ASCII space occasionally creating unnecessary empty polygons.
+- Misc: Added additional checks in EndFrame() to verify that io.KeyXXX values have not been
+  tampered with between NewFrame() and EndFrame().
 - Misc, Freetype: Fixed support for IMGUI_STB_RECT_PACK_FILENAME compile time directive
   in imgui_freetype.cpp (matching support in the regular code path). (#3062) [@DonKult]
 - Demo: Added black and white and color gradients to Demo>Examples>Custom Rendering.

imgui.cpp

@@ -3704,6 +3704,17 @@ static void NewFrameSanityChecks()
         g.IO.ConfigWindowsResizeFromEdges = false;
 }
 
+static ImGuiKeyModFlags GetMergedKeyModFlags()
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiKeyModFlags key_mod_flags = ImGuiKeyModFlags_None;
+    if (g.IO.KeyCtrl)   { key_mod_flags |= ImGuiKeyModFlags_Ctrl; }
+    if (g.IO.KeyShift)  { key_mod_flags |= ImGuiKeyModFlags_Shift; }
+    if (g.IO.KeyAlt)    { key_mod_flags |= ImGuiKeyModFlags_Alt; }
+    if (g.IO.KeySuper)  { key_mod_flags |= ImGuiKeyModFlags_Super; }
+    return key_mod_flags;
+}
+
 void ImGui::NewFrame()
 {
     IM_ASSERT(GImGui != NULL && "No current context. Did you call ImGui::CreateContext() and ImGui::SetCurrentContext() ?");
@@ -3805,6 +3816,8 @@ void ImGui::NewFrame()
     g.DragDropWithinTarget = false;
 
     // Update keyboard input state
+    // Synchronize io.KeyMods with individual modifiers io.KeyXXX bools
+    g.IO.KeyMods = GetMergedKeyModFlags();
     memcpy(g.IO.KeysDownDurationPrev, g.IO.KeysDownDuration, sizeof(g.IO.KeysDownDuration));
     for (int i = 0; i < IM_ARRAYSIZE(g.IO.KeysDown); i++)
         g.IO.KeysDownDuration[i] = g.IO.KeysDown[i] ? (g.IO.KeysDownDuration[i] < 0.0f ? 0.0f : g.IO.KeysDownDuration[i] + g.IO.DeltaTime) : -1.0f;
@@ -6720,9 +6733,15 @@ bool ImGui::DebugCheckVersionAndDataLayout(const char* version, size_t sz_io, si
 
 static void ImGui::ErrorCheckEndFrame()
 {
+    ImGuiContext& g = *GImGui;
+
+    // Verify that io.KeyXXX fields haven't been tampered with. Key mods shoudl not be modified between NewFrame() and EndFrame()
+    const ImGuiKeyModFlags expected_key_mod_flags = GetMergedKeyModFlags();
+    IM_ASSERT(g.IO.KeyMods == expected_key_mod_flags && "Mismatching io.KeyCtrl/io.KeyShift/io.KeyAlt/io.KeySuper vs io.KeyMods");
+    IM_UNUSED(expected_key_mod_flags);
+
     // Report when there is a mismatch of Begin/BeginChild vs End/EndChild calls. Important: Remember that the Begin/BeginChild API requires you
     // to always call End/EndChild even if Begin/BeginChild returns false! (this is unfortunately inconsistent with most other Begin* API).
-    ImGuiContext& g = *GImGui;
     if (g.CurrentWindowStack.Size != 1)
     {
         if (g.CurrentWindowStack.Size > 1)

imgui.h

@@ -168,6 +168,7 @@ typedef int ImGuiDragDropFlags;     // -> enum ImGuiDragDropFlags_   // Flags: f
 typedef int ImGuiFocusedFlags;      // -> enum ImGuiFocusedFlags_    // Flags: for IsWindowFocused()
 typedef int ImGuiHoveredFlags;      // -> enum ImGuiHoveredFlags_    // Flags: for IsItemHovered(), IsWindowHovered() etc.
 typedef int ImGuiInputTextFlags;    // -> enum ImGuiInputTextFlags_  // Flags: for InputText(), InputTextMultiline()
+typedef int ImGuiKeyModFlags;       // -> enum ImGuiKeyModFlags_     // Flags: for io.KeyMods (Ctrl/Shift/Alt/Super)
 typedef int ImGuiSelectableFlags;   // -> enum ImGuiSelectableFlags_ // Flags: for Selectable()
 typedef int ImGuiTabBarFlags;       // -> enum ImGuiTabBarFlags_     // Flags: for BeginTabBar()
 typedef int ImGuiTabItemFlags;      // -> enum ImGuiTabItemFlags_    // Flags: for BeginTabItem()
@@ -997,6 +998,16 @@ enum ImGuiKey_
     ImGuiKey_COUNT
 };
 
+// To test io.KeyMods (which is a combination of individual fields io.KeyCtrl, io.KeyShift, io.KeyAlt set by user/back-end)
+enum ImGuiKeyModFlags_
+{
+    ImGuiKeyModFlags_None       = 0,
+    ImGuiKeyModFlags_Ctrl       = 1 << 0,
+    ImGuiKeyModFlags_Shift      = 1 << 1,
+    ImGuiKeyModFlags_Alt        = 1 << 2,
+    ImGuiKeyModFlags_Super      = 1 << 3
+};
+
 // Gamepad/Keyboard directional navigation
 // Keyboard: Set io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard to enable. NewFrame() will automatically fill io.NavInputs[] based on your io.KeysDown[] + io.KeyMap[] arrays.
 // Gamepad:  Set io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad to enable. Back-end: set ImGuiBackendFlags_HasGamepad and fill the io.NavInputs[] fields before calling NewFrame(). Note that io.NavInputs[] is cleared by EndFrame().
@@ -1496,6 +1507,7 @@ struct ImGuiIO
     // [Internal] Dear ImGui will maintain those fields. Forward compatibility not guaranteed!
     //------------------------------------------------------------------
 
+    ImGuiKeyModFlags KeyMods;                   // Key mods flags (same as io.KeyCtrl/KeyShift/KeyAlt/KeySuper but merged into flags), updated by NewFrame()
     ImVec2      MousePosPrev;                   // Previous mouse position (note that MouseDelta is not necessary == MousePos-MousePosPrev, in case either position is invalid)
     ImVec2      MouseClickedPos[5];             // Position at time of clicking
     double      MouseClickedTime[5];            // Time of last click (used to figure out double-click)