IO: Fixed backward-compatibility accesses to io.KeysDown[]. (#4921, #4858)

+ Snuck in unrelated comments and removed the "fill once" comment (#5043)

docs/CHANGELOG.txt

@@ -39,6 +39,10 @@ Breaking changes:
 
 Other Changes:
 
+- IO: Fixed backward-compatibility regression introduced in 1.87: (#4921, #4858)
+  - Direct accesses to io.KeysDown[] with legacy indices didn't work (with new backends).
+  - Direct accesses to io.KeysDown[GetKeyIndex(XXX)] would access invalid data (with old/new backends).
+  - Calling IsKeyDown() didn't have those problems, and is recommended as io.KeysDown[] is obsolete.
 - Clipper: Fixed a regression in 1.86 when not calling clipper.End() and late destructing the
   clipper instance. High-level languages (Lua,Rust etc.) would typically be affected. (#4822)
 - IsItemHovered(): added ImGuiHoveredFlags_NoNavOverride to disable the behavior where the

imgui.cpp

@@ -1321,8 +1321,10 @@ void ImGuiIO::SetKeyEventNativeData(ImGuiKey key, int native_keycode, int native
     // Build native->imgui map so old user code can still call key functions with native 0..511 values.
 #ifndef IMGUI_DISABLE_OBSOLETE_KEYIO
     const int legacy_key = (native_legacy_index != -1) ? native_legacy_index : native_keycode;
-    if (ImGui::IsLegacyKey(legacy_key))
+    if (!ImGui::IsLegacyKey(legacy_key))
-        KeyMap[legacy_key] = key;
+        return;
+    KeyMap[legacy_key] = key;
+    KeyMap[key] = legacy_key;
 #else
     IM_UNUSED(key);
     IM_UNUSED(native_legacy_index);
@@ -3944,9 +3946,9 @@ static void ImGui::UpdateKeyboardInputs()
 #ifndef IMGUI_DISABLE_OBSOLETE_KEYIO
     if (io.BackendUsingLegacyKeyArrays == 0)
     {
-        // Backend used new io.AddKeyEvent() API: Good! Verify that old arrays are never written too.
+        // Backend used new io.AddKeyEvent() API: Good! Verify that old arrays are never written to externally.
-        for (int n = 0; n < IM_ARRAYSIZE(io.KeysDown); n++)
+        for (int n = 0; n < ImGuiKey_LegacyNativeKey_END; n++)
-            IM_ASSERT(io.KeysDown[n] == false && "Backend needs to either only use io.AddKeyEvent(), either only fill legacy io.KeysDown[] + io.KeyMap[]. Not both!");
+            IM_ASSERT((io.KeysDown[n] == false || IsKeyDown(n)) && "Backend needs to either only use io.AddKeyEvent(), either only fill legacy io.KeysDown[] + io.KeyMap[]. Not both!");
     }
     else
     {
@@ -3969,6 +3971,8 @@ static void ImGui::UpdateKeyboardInputs()
                 const ImGuiKey key = (ImGuiKey)(io.KeyMap[n] != -1 ? io.KeyMap[n] : n);
                 IM_ASSERT(io.KeyMap[n] == -1 || IsNamedKey(key));
                 io.KeysData[key].Down = io.KeysDown[n];
+                if (key != n)
+                    io.KeysDown[key] = io.KeysDown[n]; // Allow legacy code using io.KeysDown[GetKeyIndex()] with old backends
                 io.BackendUsingLegacyKeyArrays = 1;
             }
         if (io.BackendUsingLegacyKeyArrays == 1)
@@ -7875,6 +7879,13 @@ void ImGui::UpdateInputEvents(bool trickle_fast_inputs)
                     if (key == ImGuiKey_ModSuper) { io.KeySuper = keydata->Down; }
                     io.KeyMods = GetMergedKeyModFlags();
                 }
+
+                // Allow legacy code using io.KeysDown[GetKeyIndex()] with new backends
+#ifndef IMGUI_DISABLE_OBSOLETE_KEYIO
+                io.KeysDown[key] = keydata->Down;
+                if (io.KeyMap[key] != -1)
+                    io.KeysDown[io.KeyMap[key]] = keydata->Down;
+#endif
             }
         }
         else if (e->Type == ImGuiInputEventType_Text)
@@ -7967,7 +7978,7 @@ static void ImGui::ErrorCheckNewFrameSanityChecks()
     IM_ASSERT(g.Style.WindowMenuButtonPosition == ImGuiDir_None || g.Style.WindowMenuButtonPosition == ImGuiDir_Left || g.Style.WindowMenuButtonPosition == ImGuiDir_Right);
 #ifndef IMGUI_DISABLE_OBSOLETE_KEYIO
     for (int n = ImGuiKey_NamedKey_BEGIN; 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..511, or -1 for unmapped key)");
+        IM_ASSERT(g.IO.KeyMap[n] >= -1 && g.IO.KeyMap[n] < ImGuiKey_LegacyNativeKey_END && "io.KeyMap[] contains an out of bound value (need to be 0..511, or -1 for unmapped key)");
 
     // Check: required key mapping (we intentionally do NOT check all keys to not pressure user into setting up everything, but Space is required and was only added in 1.60 WIP)
     if ((g.IO.ConfigFlags & ImGuiConfigFlags_NavEnableKeyboard) && g.IO.BackendUsingLegacyKeyArrays == 1)

imgui.h

@@ -65,7 +65,7 @@ Index of this file:
 // Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals. Work in progress versions typically starts at XYY99 then bounce up to XYY00, XYY01 etc. when release tagging happens)
 #define IMGUI_VERSION               "1.88 WIP"
-#define IMGUI_VERSION_NUM           18707
+#define IMGUI_VERSION_NUM           18708
 #define IMGUI_CHECKVERSION()        ImGui::DebugCheckVersionAndDataLayout(IMGUI_VERSION, sizeof(ImGuiIO), sizeof(ImGuiStyle), sizeof(ImVec2), sizeof(ImVec4), sizeof(ImDrawVert), sizeof(ImDrawIdx))
 #define IMGUI_HAS_TABLE
 
@@ -1902,13 +1902,13 @@ struct ImGuiKeyData
 struct ImGuiIO
 {
     //------------------------------------------------------------------
-    // Configuration (fill once)                // Default value
+    // Configuration                            // Default value
     //------------------------------------------------------------------
 
     ImGuiConfigFlags   ConfigFlags;             // = 0              // See ImGuiConfigFlags_ enum. Set by user/application. Gamepad/keyboard navigation options, etc.
     ImGuiBackendFlags  BackendFlags;            // = 0              // See ImGuiBackendFlags_ enum. Set by backend (imgui_impl_xxx files or custom backend) to communicate features supported by the backend.
-    ImVec2      DisplaySize;                    // <unset>          // Main display size, in pixels (generally == GetMainViewport()->Size)
+    ImVec2      DisplaySize;                    // <unset>          // Main display size, in pixels (generally == GetMainViewport()->Size). May change every frame.
-    float       DeltaTime;                      // = 1.0f/60.0f     // Time elapsed since last frame, in seconds.
+    float       DeltaTime;                      // = 1.0f/60.0f     // Time elapsed since last frame, in seconds. May change every frame.
     float       IniSavingRate;                  // = 5.0f           // Minimum time between saving positions/sizes to .ini file, in seconds.
     const char* IniFilename;                    // = "imgui.ini"    // Path to .ini file (important: default "imgui.ini" is relative to current working dir!). Set NULL to disable automatic .ini loading/saving or if you want to manually call LoadIniSettingsXXX() / SaveIniSettingsXXX() functions.
     const char* LogFilename;                    // = "imgui_log.txt"// Path to .log file (default parameter to ImGui::LogToFile when no file is specified).
@@ -2006,7 +2006,7 @@ struct ImGuiIO
     // This is still temporarily supported as a legacy feature. However the new preferred scheme is for backend to call io.AddKeyEvent().
 #ifndef IMGUI_DISABLE_OBSOLETE_KEYIO
     int         KeyMap[ImGuiKey_COUNT];             // [LEGACY] Input: map of indices into the KeysDown[512] entries array which represent your "native" keyboard state. The first 512 are now unused and should be kept zero. Legacy backend will write into KeyMap[] using ImGuiKey_ indices which are always >512.
-    bool        KeysDown[512];                      // [LEGACY] Input: 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).
+    bool        KeysDown[ImGuiKey_COUNT];           // [LEGACY] Input: 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). This used to be [512] sized. It is now ImGuiKey_COUNT to allow legacy io.KeysDown[GetKeyIndex(...)] to work without an overflow.
 #endif
 
     //------------------------------------------------------------------
@@ -2039,7 +2039,7 @@ struct ImGuiIO
     ImU16       MouseClickedLastCount[5];           // Count successive number of clicks. Stays valid after mouse release. Reset after another click is done.
     bool        MouseReleased[5];                   // Mouse button went from Down to !Down
     bool        MouseDownOwned[5];                  // Track if button was clicked inside a dear imgui window or over void blocked by a popup. We don't request mouse capture from the application if click started outside ImGui bounds.
-    bool        MouseDownOwnedUnlessPopupClose[5];  //Track if button was clicked inside a dear imgui window.
+    bool        MouseDownOwnedUnlessPopupClose[5];  // Track if button was clicked inside a dear imgui window.
     float       MouseDownDuration[5];               // Duration the mouse button has been down (0.0f == just clicked)
     float       MouseDownDurationPrev[5];           // Previous time the mouse button has been down
     float       MouseDragMaxDistanceSqr[5];         // Squared maximum distance of how much mouse has traveled from the clicking point (used for moving thresholds)

imgui_demo.cpp

@@ -5710,6 +5710,7 @@ static void ShowDemoWindowMisc()
 #else
             struct funcs { static bool IsLegacyNativeDupe(ImGuiKey key) { return key < 512 && ImGui::GetIO().KeyMap[key] != -1; } }; // Hide Native<>ImGuiKey duplicates when both exists in the array
             const ImGuiKey key_first = 0;
+            //ImGui::Text("Legacy raw:");       for (ImGuiKey key = key_first; key < ImGuiKey_COUNT; key++) { if (io.KeysDown[key]) { ImGui::SameLine(); ImGui::Text("\"%s\" %d", ImGui::GetKeyName(key), key); } }
 #endif
             ImGui::Text("Keys down:");          for (ImGuiKey key = key_first; key < ImGuiKey_COUNT; key++) { if (funcs::IsLegacyNativeDupe(key)) continue; if (ImGui::IsKeyDown(key)) { ImGui::SameLine(); ImGui::Text("\"%s\" %d (%.02f secs)", ImGui::GetKeyName(key), key, ImGui::GetKeyData(key)->DownDuration); } }
             ImGui::Text("Keys pressed:");       for (ImGuiKey key = key_first; key < ImGuiKey_COUNT; key++) { if (funcs::IsLegacyNativeDupe(key)) continue; if (ImGui::IsKeyPressed(key)) { ImGui::SameLine(); ImGui::Text("\"%s\" %d", ImGui::GetKeyName(key), key); } }