Added ImGuiBackendFlags for backend to expose its capabilities. Added ImGuiBackendFlags_HasGamepad. (#787, #1542)

CHANGELOG.txt

@@ -76,7 +76,8 @@ Other Changes:
     - When keyboard navigation is active (io.NavActive + ImGuiConfigFlags_NavEnableKeyboard), the io.WantCaptureKeyboard flag will be set.
       For more advanced uses, you may want to read from io.NavActive or io.NavVisible. Read imgui.cpp for more details.
  - To use Gamepad Navigation:
-    - Set io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad to enable. Fill the io.NavInputs[] fields before calling NewFrame(). Note that io.NavInputs[] is cleared by EndFrame().
+    - Set io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad to enable. 
+	- Backend: Set io.BackendFlags |= ImGuiBackendFlags_HasGamepad + fill the io.NavInputs[] fields before calling NewFrame(). Note that io.NavInputs[] is cleared by EndFrame().
     - See https://github.com/ocornut/imgui/issues/1599 for recommended gamepad mapping.
     - See 'enum ImGuiNavInput_' in imgui.h for a description of inputs. Read imgui.cpp for more details.
 - Navigation: SetItemDefaultFocus() sets the navigation position in addition to scrolling. (#787)

examples/opengl3_example/imgui_impl_glfw_gl3.cpp

@@ -511,6 +511,10 @@ void ImGui_ImplGlfwGL3_NewFrame()
         MAP_ANALOG(ImGuiNavInput_LStickDown, 1,  -0.3f,  -0.9f);
         #undef MAP_BUTTON
         #undef MAP_ANALOG
+        if (axes_count > 0 && buttons_count > 0) 
+            io.BackendFlags |= ImGuiBackendFlags_HasGamepad; 
+        else 
+            io.BackendFlags &= ~ImGuiBackendFlags_HasGamepad;
     }
 
     // Start the frame. This call will update the io.WantCaptureMouse, io.WantCaptureKeyboard flag that you can use to dispatch inputs (or not) to your application.

imgui.cpp

@@ -224,7 +224,8 @@
        - or query focus information with e.g. IsWindowFocused(), IsItemFocused() etc. functions.
       Please reach out if you think the game vs navigation input sharing could be improved.
  - Gamepad:
-    - Set io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad to enable. Fill the io.NavInputs[] fields before calling NewFrame(). Note that io.NavInputs[] is cleared by EndFrame().
+    - Set io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad to enable.
+    - Backend: Set io.BackendFlags |= ImGuiBackendFlags_HasGamepad + fill the io.NavInputs[] fields before calling NewFrame(). Note that io.NavInputs[] is cleared by EndFrame().
     - See 'enum ImGuiNavInput_' in imgui.h for a description of inputs. For each entry of io.NavInputs[], set the following values:
          0.0f= not held. 1.0f= fully held. Pass intermediate 0.0f..1.0f values for analog triggers/sticks.
     - We uses a simple >0.0f test for activation testing, and won't attempt to test for a dead-zone.
@@ -846,9 +847,10 @@ ImGuiIO::ImGuiIO()
     memset(this, 0, sizeof(*this));
 
     // Settings
+    ConfigFlags = 0x00;
+    BackendFlags = 0x00;
     DisplaySize = ImVec2(-1.0f, -1.0f);
     DeltaTime = 1.0f/60.0f;
-    ConfigFlags = 0x00;
     IniSavingRate = 5.0f;
     IniFilename = "imgui.ini";
     LogFilename = "imgui_log.txt";
@@ -2958,7 +2960,7 @@ static void ImGui::NavUpdate()
     if (g.NavScoringCount > 0) printf("[%05d] NavScoringCount %d for '%s' layer %d (Init:%d, Move:%d)\n", g.FrameCount, g.NavScoringCount, g.NavWindow ? g.NavWindow->Name : "NULL", g.NavLayer, g.NavInitRequest || g.NavInitResultId != 0, g.NavMoveRequest);
 #endif
 
-    if (g.IO.ConfigFlags & ImGuiConfigFlags_NavEnableGamepad)
+    if ((g.IO.ConfigFlags & ImGuiConfigFlags_NavEnableGamepad) && (g.IO.BackendFlags & ImGuiBackendFlags_HasGamepad))
         if (g.IO.NavInputs[ImGuiNavInput_Activate] > 0.0f || g.IO.NavInputs[ImGuiNavInput_Input] > 0.0f || g.IO.NavInputs[ImGuiNavInput_Cancel] > 0.0f || g.IO.NavInputs[ImGuiNavInput_Menu] > 0.0f)
             g.NavInputSource = ImGuiInputSource_NavGamepad;
 
@@ -3055,7 +3057,9 @@ static void ImGui::NavUpdate()
     NavUpdateWindowing();
 
     // Set output flags for user application
-    g.IO.NavActive = (g.IO.ConfigFlags & (ImGuiConfigFlags_NavEnableGamepad | ImGuiConfigFlags_NavEnableKeyboard)) && g.NavWindow && !(g.NavWindow->Flags & ImGuiWindowFlags_NoNavInputs);
+    bool nav_keyboard_active = (g.IO.ConfigFlags & ImGuiConfigFlags_NavEnableKeyboard) != 0;
+    bool nav_gamepad_active = (g.IO.ConfigFlags & ImGuiConfigFlags_NavEnableGamepad) != 0 && (g.IO.BackendFlags & ImGuiBackendFlags_HasGamepad) != 0;
+    g.IO.NavActive = (nav_keyboard_active || nav_gamepad_active) && g.NavWindow && !(g.NavWindow->Flags & ImGuiWindowFlags_NoNavInputs);
     g.IO.NavVisible = (g.IO.NavActive && g.NavId != 0 && !g.NavDisableHighlight) || (g.NavWindowingTarget != NULL) || g.NavInitRequest;
 
     // Process NavCancel input (to close a popup, get back to parent, clear focus)

imgui.h

@@ -91,6 +91,7 @@ typedef int ImGuiStyleVar;          // enum: a variable identifier for styling
 typedef int ImDrawCornerFlags;      // flags: for ImDrawList::AddRect*() etc.   // enum ImDrawCornerFlags_
 typedef int ImDrawListFlags;        // flags: for ImDrawList                    // enum ImDrawListFlags_
 typedef int ImFontAtlasFlags;       // flags: for ImFontAtlas                   // enum ImFontAtlasFlags_
+typedef int ImGuiBackendFlags;      // flags: for io.BackendFlags               // enum ImGuiBackendFlags_
 typedef int ImGuiColorEditFlags;    // flags: for ColorEdit*(), ColorPicker*()  // enum ImGuiColorEditFlags_
 typedef int ImGuiColumnsFlags;      // flags: for *Columns*()                   // enum ImGuiColumnsFlags_
 typedef int ImGuiConfigFlags;       // flags: for io.ConfigFlags                // enum ImGuiConfigFlags_
@@ -736,7 +737,7 @@ enum ImGuiKey_
 
 // [BETA] Gamepad/Keyboard directional navigation
 // Keyboard: Set io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard to enable. NewFrame() will automatically fill io.NavInputs[] based on your io.KeyDown[] + io.KeyMap[] arrays.
-// Gamepad:  Set io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad to enable. Fill the io.NavInputs[] fields before calling NewFrame(). Note that io.NavInputs[] is cleared by EndFrame().
+// 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().
 // Read instructions in imgui.cpp for more details. Download PNG/PSD at goo.gl/9LgVZW.
 enum ImGuiNavInput_
 {
@@ -769,17 +770,23 @@ enum ImGuiNavInput_
     ImGuiNavInput_InternalStart_ = ImGuiNavInput_KeyMenu_
 };
 
-// Configuration flags stored in io.ConfigFlags
+// Configuration flags stored in io.ConfigFlags. Set by user/application.
 enum ImGuiConfigFlags_
 {
     ImGuiConfigFlags_NavEnableKeyboard      = 1 << 0,   // Master keyboard navigation enable flag. NewFrame() will automatically fill io.NavInputs[] based on io.KeyDown[].
-    ImGuiConfigFlags_NavEnableGamepad     = 1 << 1,   // Master gamepad navigation enable flag. This is mostly to instruct your imgui back-end to fill io.NavInputs[].
+    ImGuiConfigFlags_NavEnableGamepad       = 1 << 1,   // Master gamepad navigation enable flag. This is mostly to instruct your imgui back-end to fill io.NavInputs[]. Back-end also needs to set ImGuiBackendFlags_HasGamepad.
     ImGuiConfigFlags_NavEnableSetMousePos   = 1 << 2,   // Request navigation to allow moving the mouse cursor. May be useful on TV/console systems where moving a virtual mouse is awkward. Will update io.MousePos and set io.WantSetMousePos=true. If enabled you MUST honor io.WantSetMousePos requests in your binding, otherwise ImGui will react as if the mouse is jumping around back and forth.
     ImGuiConfigFlags_NavNoCaptureKeyboard   = 1 << 3,   // Do not set the io.WantCaptureKeyboard flag with io.NavActive is set. 
 
     // User storage (to allow your back-end/engine to communicate to code that may be shared between multiple projects. Those flags are not used by core ImGui)
-    ImGuiConfigFlags_IsSRGB               = 1 << 20,  // Back-end is SRGB-aware.
+    ImGuiConfigFlags_IsSRGB                 = 1 << 20,  // Application is SRGB-aware.
-    ImGuiConfigFlags_IsTouchScreen        = 1 << 21   // Back-end is using a touch screen instead of a mouse.
+    ImGuiConfigFlags_IsTouchScreen          = 1 << 21   // Application is using a touch screen instead of a mouse.
+};
+
+// Back-end capabilities flags stored in io.BackendFlags. Set by imgui_impl_xxx or custom back-end.
+enum ImGuiBackendFlags_
+{
+    ImGuiBackendFlags_HasGamepad            = 1 << 0    // Back-end has a connected gamepad
 };
 
 // Enumeration for PushStyleColor() / PopStyleColor()
@@ -986,9 +993,10 @@ struct ImGuiIO
     // Settings (fill once)                 // Default value:
     //------------------------------------------------------------------
 
+    ImGuiConfigFlags   ConfigFlags;         // = 0                  // See ImGuiConfigFlags_ enum. Set by user/application. Gamepad/keyboard navigation options, etc.
+    ImGuiBackendFlags  BackendFlags;        // = 0                  // Set ImGuiBackendFlags_ enum. Set by imgui_impl_xxx files or custom back-end.
     ImVec2        DisplaySize;              // <unset>              // Display size, in pixels. For clamping windows positions.
     float         DeltaTime;                // = 1.0f/60.0f         // Time elapsed since last frame, in seconds.
-    ImGuiConfigFlags ConfigFlags;           // = 0                  // See ImGuiConfigFlags_ enum. Gamepad/keyboard navigation options, etc.
     float         IniSavingRate;            // = 5.0f               // Maximum time between saving positions/sizes to .ini file, in seconds.
     const char*   IniFilename;              // = "imgui.ini"        // Path to .ini file. NULL to disable .ini saving.
     const char*   LogFilename;              // = "imgui_log.txt"    // Path to .log file (default parameter to ImGui::LogToFile when no file is specified).