NewFrame(): Added an assert to detect incorrect filling of the io.KeyMap[] array earlier. (#1555) + comments.

imgui.cpp

@@ -2282,6 +2282,8 @@ void ImGui::NewFrame()
     IM_ASSERT(g.Style.CurveTessellationTol > 0.0f                       && "Invalid style setting");
     IM_ASSERT(g.Style.Alpha >= 0.0f && g.Style.Alpha <= 1.0f            && "Invalid style setting. Alpha cannot be negative (allows us to avoid a few clamps in color computations)");
     IM_ASSERT((g.FrameCount == 0 || g.FrameCountEnded == g.FrameCount)  && "Forgot to call Render() or EndFrame() at the end of the previous frame?");
+    for (int n = 0; n < ImGuiKey_COUNT; n++)
+        IM_ASSERT(g.IO.KeyMap[n] >= -1 && g.IO.KeyMap[n] < IM_ARRAYSIZE(g.IO.KeysDown) && "io.KeyMap[] contains an out of bound value (need to be 0..512, or -1 for unmapped key)");
 
     // Initialize on first frame
     if (!g.Initialized)

imgui.h

@@ -881,8 +881,8 @@ struct ImGuiIO
     const char*   LogFilename;              // = "imgui_log.txt"    // Path to .log file (default parameter to ImGui::LogToFile when no file is specified).
     float         MouseDoubleClickTime;     // = 0.30f              // Time for a double-click, in seconds.
     float         MouseDoubleClickMaxDist;  // = 6.0f               // Distance threshold to stay in to validate a double-click, in pixels.
-    float         MouseDragThreshold;       // = 6.0f               // Distance threshold before considering we are dragging
-    int           KeyMap[ImGuiKey_COUNT];   // <unset>              // Map of indices into the KeysDown[512] entries array
+    float         MouseDragThreshold;       // = 6.0f               // Distance threshold before considering we are dragging.
+    int           KeyMap[ImGuiKey_COUNT];   // <unset>              // Map of indices into the KeysDown[512] entries array which represent your "native" keyboard state.
     float         KeyRepeatDelay;           // = 0.250f             // When holding a key/button, time before it starts repeating, in seconds (for buttons in Repeat mode, etc.).
     float         KeyRepeatRate;            // = 0.050f             // When holding a key/button, rate at which it repeats, in seconds.
     void*         UserData;                 // = NULL               // Store your own data for retrieval by callbacks.
@@ -936,7 +936,7 @@ struct ImGuiIO
     bool        KeyShift;                   // Keyboard modifier pressed: Shift
     bool        KeyAlt;                     // Keyboard modifier pressed: Alt
     bool        KeySuper;                   // Keyboard modifier pressed: Cmd/Super/Windows
-    bool        KeysDown[512];              // Keyboard keys that are pressed (in whatever storage order you naturally have access to keyboard data)
+    bool        KeysDown[512];              // Keyboard keys that are pressed (ideally left in the "native" order your engine has access to keyboard keys, so you can use your own defines/enums for keys).
     ImWchar     InputCharacters[16+1];      // List of characters input (translated by user from keypress+keyboard state). Fill using AddInputCharacter() helper.
 
     // Functions