Added IsMouseDragging(), GetMouseDragDelta() given button and lock threshold. added io.MouseDragThreshold setting. (#167)

Removed GetItemActiveDragDelta()

imgui.cpp

@@ -577,6 +577,7 @@ ImGuiIO::ImGuiIO()
     MousePosPrev = ImVec2(-1,-1);
     MouseDoubleClickTime = 0.30f;
     MouseDoubleClickMaxDist = 6.0f;
+    MouseDragThreshold = 6.0f;
     UserData = NULL;
 
     // User functions
@@ -1840,6 +1841,11 @@ void ImGui::NewFrame()
                 g.IO.MouseClickedTime[i] = g.Time;
             }
             g.IO.MouseClickedPos[i] = g.IO.MousePos;
+            g.IO.MouseDragMaxDistanceSqr[i] = 0.0f;
+        }
+        else if (g.IO.MouseDown[i])
+        {
+            g.IO.MouseDragMaxDistanceSqr[i] = ImMax(g.IO.MouseDragMaxDistanceSqr[i], ImLengthSqr(g.IO.MousePos - g.IO.MouseClickedPos[i]));
         }
     }
     for (size_t i = 0; i < IM_ARRAYSIZE(g.IO.KeysDown); i++)
@@ -2539,16 +2545,29 @@ bool ImGui::IsMouseDoubleClicked(int button)
     return g.IO.MouseDoubleClicked[button];
 }
 
+bool ImGui::IsMouseDragging(int button, float lock_threshold)
+{
+    ImGuiState& g = *GImGui;
+    IM_ASSERT(button >= 0 && button < IM_ARRAYSIZE(g.IO.MouseDown));
+    if (lock_threshold < 0.0f)
+        lock_threshold = g.IO.MouseDragThreshold;
+    return g.IO.MouseDragMaxDistanceSqr[button] >= lock_threshold * lock_threshold;
+}
+
 ImVec2 ImGui::GetMousePos()
 {
     return GImGui->IO.MousePos;
 }
 
-ImVec2 ImGui::GetMouseDragDelta()
+ImVec2 ImGui::GetMouseDragDelta(int button, float lock_threshold)
 {
     ImGuiState& g = *GImGui;
-    if (g.IO.MouseDown[0])
+    IM_ASSERT(button >= 0 && button < IM_ARRAYSIZE(g.IO.MouseDown));
-        return g.IO.MousePos - g.IO.MouseClickedPos[0];     // Assume we can only get active with left-mouse button (at the moment).
+    if (lock_threshold < 0.0f)
+        lock_threshold = g.IO.MouseDragThreshold;
+    if (g.IO.MouseDown[button])
+        if (g.IO.MouseDragMaxDistanceSqr[button] >= lock_threshold * lock_threshold)
+            return g.IO.MousePos - g.IO.MouseClickedPos[button];     // Assume we can only get active with left-mouse button (at the moment).
     return ImVec2(0.0f, 0.0f);
 }
 
@@ -2581,17 +2600,6 @@ bool ImGui::IsAnyItemActive()
     return g.ActiveId != 0;
 }
 
-ImVec2 ImGui::GetItemActiveDragDelta()
-{
-    if (ImGui::IsItemActive())
-    {
-        ImGuiState& g = *GImGui;
-        if (g.IO.MouseDown[0])
-            return g.IO.MousePos - g.IO.MouseClickedPos[0];     // Assume we can only get active with left-mouse button (at the moment).
-    }
-    return ImVec2(0.0f, 0.0f);
-}
-
 ImVec2 ImGui::GetItemRectMin()
 {
     ImGuiWindow* window = GetCurrentWindow();
@@ -9417,11 +9425,13 @@ void ImGui::ShowTestWindow(bool* opened)
         if (ImGui::TreeNode("Dragging"))
         {
             // You can use ImGui::GetItemActiveDragDelta() to query for the dragged amount on any widget.
-            static ImVec2 value(0.0f, 0.0f);
+            static ImVec2 value_raw(0.0f, 0.0f);
+            static ImVec2 value_with_lock_threshold(0.0f, 0.0f);
             ImGui::Button("Drag Me");
             if (ImGui::IsItemActive())
             {
-                value = ImGui::GetItemActiveDragDelta();
+                value_raw = ImGui::GetMouseDragDelta(0, 0.0f);
+                value_with_lock_threshold = ImGui::GetMouseDragDelta(0);
                 //ImGui::SetTooltip("Delta: %.1f, %.1f", value.x, value.y);
 
                 // Draw a line between the button and the mouse cursor
@@ -9430,7 +9440,7 @@ void ImGui::ShowTestWindow(bool* opened)
                 draw_list->AddLine(ImGui::CalcItemRectClosestPoint(ImGui::GetIO().MousePos, true, -2.0f), ImGui::GetIO().MousePos, ImColor(ImGui::GetStyle().Colors[ImGuiCol_Button]), 2.0f);
                 draw_list->PopClipRect();
             }
-            ImGui::SameLine(); ImGui::Text("Value: %.1f, %.1f", value.x, value.y);
+            ImGui::SameLine(); ImGui::Text("Raw (%.1f, %.1f), WithLockThresold (%.1f, %.1f)", value_raw.x, value_raw.y, value_with_lock_threshold.x, value_with_lock_threshold.y);
             ImGui::TreePop();
         }
     }

imgui.h

@@ -355,7 +355,6 @@ namespace ImGui
     IMGUI_API bool          IsItemHoveredRectOnly();                                            // was the last item hovered by mouse? even if another item is active while we are hovering this.
     IMGUI_API bool          IsItemActive();                                                     // was the last item active? (e.g. button being held, text field being edited- items that don't interact will always return false)
     IMGUI_API bool          IsAnyItemActive();                                                  // 
-    IMGUI_API ImVec2        GetItemActiveDragDelta();                                           // mouse delta from the time the item first got active
     IMGUI_API ImVec2        GetItemRectMin();                                                   // get bounding rect of last item
     IMGUI_API ImVec2        GetItemRectMax();                                                   // "
     IMGUI_API ImVec2        GetItemRectSize();                                                  // "
@@ -369,9 +368,10 @@ namespace ImGui
     IMGUI_API bool          IsMouseHoveringWindow();                                            // is mouse hovering current window ("window" in API names always refer to current window)
     IMGUI_API bool          IsMouseHoveringAnyWindow();                                         // is mouse hovering any active imgui window
     IMGUI_API bool          IsMouseHoveringRect(const ImVec2& rect_min, const ImVec2& rect_max);// is mouse hovering given bounding rect
+    IMGUI_API bool          IsMouseDragging(int button = 0, float lock_threshold = -1.0f);      // is mouse dragging. if lock_threshold < -1.0f uses io.MouseDraggingThreshold.
     IMGUI_API bool          IsPosHoveringAnyWindow(const ImVec2& pos);                          // is given position hovering any active imgui window
     IMGUI_API ImVec2        GetMousePos();                                                      // shortcut to ImGui::GetIO().MousePos provided by user, to be consistent with other calls
-    IMGUI_API ImVec2        GetMouseDragDelta();                                                // dragging amount - also see: GetItemActiveDragDelta().
+    IMGUI_API ImVec2        GetMouseDragDelta(int button = 0, float lock_threshold = -1.0f);    // dragging amount, also see: GetItemActiveDragDelta(). if lock_threshold < -1.0f uses io.MouseDraggingThreshold.
     IMGUI_API float         GetTime();
     IMGUI_API int           GetFrameCount();
     IMGUI_API const char*   GetStyleColName(ImGuiCol idx);
@@ -581,6 +581,7 @@ 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
     void*         UserData;                 // = NULL               // Store your own data for retrieval by callbacks.
 
@@ -650,6 +651,7 @@ struct ImGuiIO
     bool        MouseDoubleClicked[5];      // Has mouse button been double-clicked?
     bool        MouseDownOwned[5];          // Track if button was clicked inside a window. We don't request mouse capture from the application if click started outside ImGui bounds.
     float       MouseDownTime[5];           // Time the mouse button has been down
+    float       MouseDragMaxDistanceSqr[5]; // Squared maximum distance of how much mouse has traveled from the click point
     float       KeysDownTime[512];          // Time the keyboard key has been down
 
     IMGUI_API   ImGuiIO();