Merge branch 'master' into docking

# Conflicts:
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_dx12.cpp
#	examples/imgui_impl_dx9.cpp
#	examples/imgui_impl_opengl2.cpp
#	examples/imgui_impl_opengl3.cpp
#	examples/imgui_impl_vulkan.cpp
#	imgui.cpp

imgui.h

@@ -300,7 +300,6 @@ namespace ImGui
     // - Those functions are bound to be redesigned soon (they are confusing, incomplete and return values in local window coordinates which increases confusion)
     IMGUI_API ImVec2        GetContentRegionMax();                                          // current content boundaries (typically window boundaries including scrolling, or current column boundaries), in windows coordinates
     IMGUI_API ImVec2        GetContentRegionAvail();                                        // == GetContentRegionMax() - GetCursorPos()
-    IMGUI_API float         GetContentRegionAvailWidth();                                   // == GetContentRegionAvail().x
     IMGUI_API ImVec2        GetWindowContentRegionMin();                                    // content boundaries min (roughly (0,0)-Scroll), in window coordinates
     IMGUI_API ImVec2        GetWindowContentRegionMax();                                    // content boundaries max (roughly (0,0)+Size-Scroll) where Size can be override with SetNextWindowContentSize(), in window coordinates
     IMGUI_API float         GetWindowContentRegionWidth();                                  //
@@ -1621,6 +1620,8 @@ struct ImGuiWindowClass
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
 namespace ImGui
 {
+    // OBSOLETED in 1.70 (from May 2019)
+    static inline float GetContentRegionAvailWidth()          { return GetContentRegionAvail().x; }
     // OBSOLETED in 1.69 (from Mar 2019)
     static inline ImDrawList* GetOverlayDrawList()            { return GetForegroundDrawList(); }
     // OBSOLETED in 1.66 (from Sep 2018)
@@ -1850,11 +1851,18 @@ struct ImColor
 
 // Draw callbacks for advanced uses.
 // NB: You most likely do NOT need to use draw callbacks just to create your own widget or customized UI rendering,
-// you can poke into the draw list for that! Draw callback may be useful for example to: A) Change your GPU render state,
-// B) render a complex 3D scene inside a UI element without an intermediate texture/render target, etc.
+// you can poke into the draw list for that! Draw callback may be useful for example to: 
+//  A) Change your GPU render state,
+//  B) render a complex 3D scene inside a UI element without an intermediate texture/render target, etc.
 // The expected behavior from your rendering function is 'if (cmd.UserCallback != NULL) { cmd.UserCallback(parent_list, cmd); } else { RenderTriangles() }'
 typedef void (*ImDrawCallback)(const ImDrawList* parent_list, const ImDrawCmd* cmd);
 
+// Special Draw Callback value to request renderer back-end to reset the graphics/render state.
+// The renderer back-end needs to handle this special value, otherwise it will crash trying to call a function at this address.
+// This is useful for example if you submitted callbacks which you know have altered the render state and you want it to be restored.
+// It is not done by default because they are many perfectly useful way of altering render state for imgui contents (e.g. changing shader/blending settings before an Image call).
+#define ImDrawCallback_ResetRenderState     (ImDrawCallback)(-1)
+
 // Typically, 1 command = 1 GPU draw call (unless command is a callback)
 struct ImDrawCmd
 {