DragFloat, DragInt: very slightly increased mouse drag threshold + expressing it as a factor of default value + disabled experimental click-to-input on DragXXX functions. (#3737)

docs/CHANGELOG.txt

@@ -92,6 +92,7 @@ Other Changes:
   where the byte count is unchanged but the decoded character count changes. (#3587) [@gqw]
 - InputText: Fixed swiching from single to multi-line while preserving same ID.
 - Combo: Fixed using IsItemEdited() after Combo() not matching the return value from Combo(). (#2034)
+- DragFloat, DragInt: very slightly increased mouse drag threshold + expressing it as a factor of default value.
 - Nav: Fixed IsItemFocused() from returning false when Nav highlight is hidden because mouse has moved.
   It's essentially been always the case but it doesn't make much sense. Instead we will aim at exposing
   feedback and control of keyboard/gamepad navigation highlight and mouse hover disable flag. (#787, #2048)

imgui_widgets.cpp

@@ -86,6 +86,10 @@ Index of this file:
 // Data
 //-------------------------------------------------------------------------
 
+// Widgets
+static const float          DRAGDROP_HOLD_TO_OPEN_TIMER = 0.70f;    // Time for drag-hold to activate items accepting the ImGuiButtonFlags_PressedOnDragDropHold button behavior.
+static const float          DRAG_MOUSE_THRESHOLD_FACTOR = 0.50f;    // Multiplier for the default value of io.MouseDragThreshold to make DragFloat/DragInt react faster to mouse drags.
+
 // Those MIN/MAX values are not define because we need to point to them
 static const signed char    IM_S8_MIN  = -128;
 static const signed char    IM_S8_MAX  = 127;
@@ -516,10 +520,9 @@ bool ImGui::ButtonBehavior(const ImRect& bb, ImGuiID id, bool* out_hovered, bool
     if (g.DragDropActive && (flags & ImGuiButtonFlags_PressedOnDragDropHold) && !(g.DragDropSourceFlags & ImGuiDragDropFlags_SourceNoHoldToOpenOthers))
         if (IsItemHovered(ImGuiHoveredFlags_AllowWhenBlockedByActiveItem))
         {
-            const float DRAG_DROP_HOLD_TIMER = 0.70f;
             hovered = true;
             SetHoveredID(id);
-            if (CalcTypematicRepeatAmount(g.HoveredIdTimer + 0.0001f - g.IO.DeltaTime, g.HoveredIdTimer + 0.0001f, DRAG_DROP_HOLD_TIMER, 0.00f))
+            if (CalcTypematicRepeatAmount(g.HoveredIdTimer + 0.0001f - g.IO.DeltaTime, g.HoveredIdTimer + 0.0001f, DRAGDROP_HOLD_TO_OPEN_TIMER, 0.00f))
             {
                 pressed = true;
                 g.DragDropHoldJustPressedId = id;
@@ -2108,7 +2111,7 @@ bool ImGui::DragBehaviorT(ImGuiDataType data_type, TYPE* v, float v_speed, const
 
     // Inputs accumulates into g.DragCurrentAccum, which is flushed into the current value as soon as it makes a difference with our precision settings
     float adjust_delta = 0.0f;
-    if (g.ActiveIdSource == ImGuiInputSource_Mouse && IsMousePosValid() && g.IO.MouseDragMaxDistanceSqr[0] > 1.0f * 1.0f)
+    if (g.ActiveIdSource == ImGuiInputSource_Mouse && IsMousePosValid() && IsMouseDragPastThreshold(0, g.IO.MouseDragThreshold * DRAG_MOUSE_THRESHOLD_FACTOR))
     {
         adjust_delta = g.IO.MouseDelta[axis];
         if (g.IO.KeyAlt)
@@ -2271,7 +2274,7 @@ bool ImGui::DragScalar(const char* label, ImGuiDataType data_type, void* p_data,
     else if (data_type == ImGuiDataType_S32 && strcmp(format, "%d") != 0) // (FIXME-LEGACY: Patch old "%.0f" format string to use "%d", read function more details.)
         format = PatchFormatStringFloatToInt(format);
 
-    // Tabbing or CTRL-clicking on Drag turns it into an input box
+    // Tabbing or CTRL-clicking on Drag turns it into an InputText
     const bool hovered = ItemHoverable(frame_bb, id);
     const bool temp_input_allowed = (flags & ImGuiSliderFlags_NoInput) == 0;
     bool temp_input_is_active = temp_input_allowed && TempInputIsActive(id);
@@ -2292,6 +2295,17 @@ bool ImGui::DragScalar(const char* label, ImGuiDataType data_type, void* p_data,
                 FocusableItemUnregister(window);
             }
         }
+#if 0
+        // Experimental: simple click (without moving) turns Drag into an InputText
+        // FIXME: Currently polling ImGuiConfigFlags_IsTouchScreen, may either poll an hypothetical ImGuiBackendFlags_HasKeyboard and/or an explicit drag settings.
+        if (temp_input_allowed && !temp_input_is_active && !(g.IO.ConfigFlags & ImGuiConfigFlags_IsTouchScreen))
+            if (g.ActiveId == id && hovered && g.IO.MouseReleased[0] && !IsMouseDragPastThreshold(0, g.IO.MouseDragThreshold * DRAG_MOUSE_THRESHOLD_FACTOR))
+            {
+                g.NavInputId = id;
+                temp_input_is_active = true;
+                FocusableItemUnregister(window);
+            }
+#endif
     }
 
     if (temp_input_is_active)