SameLine() with explicit X position is relative to left of group/colu…

…mns (ref #746, #125, #630)

imgui.cpp

@@ -150,6 +150,7 @@
  Here is a change-log of API breaking changes, if you are using one of the functions listed, expect to have to fix some code.
  Also read releases logs https://github.com/ocornut/imgui/releases for more details.
 
+ - 2016/07/30 (1.50) - SameLine(x) with x>0.0f is now relative to left of column/group if any, and not always to left of window. This was sort of always the intent and hopefully breakage should be minimal.
  - 2016/05/12 (1.49) - title bar (using ImGuiCol_TitleBg/ImGuiCol_TitleBgActive colors) isn't rendered over a window background (ImGuiCol_WindowBg color) anymore. 
                        If your TitleBg/TitleBgActive alpha was 1.0f or you are using the default theme it will not affect you. 
                        However if your TitleBg/TitleBgActive alpha was <1.0f you need to tweak your custom theme to readjust for the fact that we don't draw a WindowBg background behind the title bar.
@@ -4221,6 +4222,7 @@ bool ImGui::Begin(const char* name, bool* p_open, const ImVec2& size_on_first_us
 
         // Setup drawing context
         window->DC.IndentX = 0.0f + window->WindowPadding.x - window->Scroll.x;
+        window->DC.GroupOffsetX = 0.0f;
         window->DC.ColumnsOffsetX = 0.0f;
         window->DC.CursorStartPos = window->Pos + ImVec2(window->DC.IndentX + window->DC.ColumnsOffsetX, window->TitleBarHeight() + window->MenuBarHeight() + window->WindowPadding.y - window->Scroll.y);
         window->DC.CursorPos = window->DC.CursorStartPos;
@@ -9116,7 +9118,8 @@ void ImGui::BeginGroup()
     group_data.BackupLogLinePosY = window->DC.LogLinePosY;
     group_data.AdvanceCursor = true;
 
-    window->DC.IndentX = window->DC.CursorPos.x - window->Pos.x - window->DC.ColumnsOffsetX;
+    window->DC.GroupOffsetX = window->DC.CursorPos.x - window->Pos.x - window->DC.ColumnsOffsetX;
+    window->DC.IndentX = window->DC.GroupOffsetX;
     window->DC.CursorMaxPos = window->DC.CursorPos;
     window->DC.CurrentLineHeight = 0.0f;
     window->DC.LogLinePosY = window->DC.CursorPos.y - 9999.0f;
@@ -9140,6 +9143,7 @@ void ImGui::EndGroup()
     window->DC.CurrentLineHeight = group_data.BackupCurrentLineHeight;
     window->DC.CurrentLineTextBaseOffset = group_data.BackupCurrentLineTextBaseOffset;
     window->DC.IndentX = group_data.BackupIndentX;
+    window->DC.GroupOffsetX = window->DC.IndentX;
     window->DC.LogLinePosY = window->DC.CursorPos.y - 9999.0f;
 
     if (group_data.AdvanceCursor)
@@ -9156,7 +9160,7 @@ void ImGui::EndGroup()
 
 // Gets back to previous line and continue with horizontal layout
 //      pos_x == 0      : follow right after previous item
-//      pos_x != 0      : align to specified x position
+//      pos_x != 0      : align to specified x position (relative to window/group left)
 //      spacing_w < 0   : use default spacing if pos_x == 0, no spacing if pos_x != 0
 //      spacing_w >= 0  : enforce spacing amount
 void ImGui::SameLine(float pos_x, float spacing_w)
@@ -9169,7 +9173,7 @@ void ImGui::SameLine(float pos_x, float spacing_w)
     if (pos_x != 0.0f)
     {
         if (spacing_w < 0.0f) spacing_w = 0.0f;
-        window->DC.CursorPos.x = window->Pos.x - window->Scroll.x + pos_x + spacing_w;
+        window->DC.CursorPos.x = window->Pos.x - window->Scroll.x + pos_x + spacing_w + window->DC.GroupOffsetX + window->DC.ColumnsOffsetX;
         window->DC.CursorPos.y = window->DC.CursorPosPrevLine.y;
     }
     else
@@ -9352,7 +9356,7 @@ void ImGui::Columns(int columns_count, const char* id, bool border)
             if (held)
             {
                 if (g.ActiveIdIsJustActivated)
-                    g.ActiveIdClickOffset.x -= 4;   // Store from center of column line
+                    g.ActiveIdClickOffset.x -= 4;   // Store from center of column line (we used a 8 wide rect for columns clicking)
                 x = GetDraggedColumnOffset(i);
                 SetColumnOffset(i, x);
             }

imgui_internal.h

@@ -546,6 +546,7 @@ struct IMGUI_API ImGuiDrawContext
     int                     StackSizesBackup[6];    // Store size of various stacks for asserting
 
     float                   IndentX;                // Indentation / start position from left of window (increased by TreePush/TreePop, etc.)
+    float                   GroupOffsetX;
     float                   ColumnsOffsetX;         // Offset to the current column (if ColumnsCurrent > 0). FIXME: This and the above should be a stack to allow use cases like Tree->Column->Tree. Need revamp columns API.
     int                     ColumnsCurrent;
     int                     ColumnsCount;