TreeNode: added ImGuiTreeNodeFlags_DrawTreeXXX flags. (#2920)

# Conflicts:
#	docs/CHANGELOG.txt

imgui.h

@@ -1214,6 +1214,12 @@ enum ImGuiTreeNodeFlags_
     ImGuiTreeNodeFlags_NavLeftJumpsBackHere = 1 << 17,  // (WIP) Nav: left direction may move to this TreeNode() from any of its child (items submitted between TreeNode and TreePop)
     ImGuiTreeNodeFlags_CollapsingHeader     = ImGuiTreeNodeFlags_Framed | ImGuiTreeNodeFlags_NoTreePushOnOpen | ImGuiTreeNodeFlags_NoAutoOpenOnLog,
 
+    // [EXPERIMENTAL] Draw lines connecting TreeNode hierarchy. Discuss in GitHub issue #2920.
+    // Default value is pulled from style.TreeLinesFlags. May be overridden in TreeNode calls.
+    ImGuiTreeNodeFlags_DrawLinesNone        = 1 << 18,  // No lines drawn
+    ImGuiTreeNodeFlags_DrawLinesFull        = 1 << 19,  // Horizontal lines to child nodes. Vertical line drawn down to TreePop() position: cover full contents.
+    ImGuiTreeNodeFlags_DrawLinesToNodes     = 1 << 20,  // Horizontal lines to child nodes. Vertical line drawn down to bottom-most child node. A little bit slower.
+
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
     ImGuiTreeNodeFlags_AllowItemOverlap     = ImGuiTreeNodeFlags_AllowOverlap,  // Renamed in 1.89.7
     ImGuiTreeNodeFlags_SpanTextWidth        = ImGuiTreeNodeFlags_SpanLabelWidth,// Renamed in 1.90.7
@@ -1666,7 +1672,8 @@ enum ImGuiCol_
     ImGuiCol_TableRowBg,            // Table row background (even rows)
     ImGuiCol_TableRowBgAlt,         // Table row background (odd rows)
     ImGuiCol_TextLink,              // Hyperlink color
-    ImGuiCol_TextSelectedBg,
+    ImGuiCol_TextSelectedBg,        // Selected text inside an InputText
+    ImGuiCol_TreeLines,             // Tree node hierarchy outlines when using ImGuiTreeNodeFlags_DrawLines
     ImGuiCol_DragDropTarget,        // Rectangle highlighting a drop target
     ImGuiCol_NavCursor,             // Color of keyboard/gamepad navigation cursor/rectangle, when visible
     ImGuiCol_NavWindowingHighlight, // Highlight window when using CTRL+TAB
@@ -1722,6 +1729,7 @@ enum ImGuiStyleVar_
     ImGuiStyleVar_TabBarOverlineSize,       // float     TabBarOverlineSize
     ImGuiStyleVar_TableAngledHeadersAngle,  // float     TableAngledHeadersAngle
     ImGuiStyleVar_TableAngledHeadersTextAlign,// ImVec2  TableAngledHeadersTextAlign
+    ImGuiStyleVar_TreeLinesSize,            // float     TreeLinesSize
     ImGuiStyleVar_ButtonTextAlign,          // ImVec2    ButtonTextAlign
     ImGuiStyleVar_SelectableTextAlign,      // ImVec2    SelectableTextAlign
     ImGuiStyleVar_SeparatorTextBorderSize,  // float     SeparatorTextBorderSize
@@ -2181,6 +2189,8 @@ struct ImGuiStyle
     float       TabBarOverlineSize;         // Thickness of tab-bar overline, which highlights the selected tab-bar.
     float       TableAngledHeadersAngle;    // Angle of angled headers (supported values range from -50.0f degrees to +50.0f degrees).
     ImVec2      TableAngledHeadersTextAlign;// Alignment of angled headers within the cell
+    ImGuiTreeNodeFlags TreeLinesFlags;      // Default way to draw lines connecting TreeNode hierarchy. ImGuiTreeNodeFlags_DrawLinesNone or ImGuiTreeNodeFlags_DrawLinesFull or ImGuiTreeNodeFlags_DrawLinesToNodes.
+    float              TreeLinesSize;       // Thickness of outlines when using ImGuiTreeNodeFlags_DrawLines.
     ImGuiDir    ColorButtonPosition;        // Side of the color button in the ColorEdit4 widget (left/right). Defaults to ImGuiDir_Right.
     ImVec2      ButtonTextAlign;            // Alignment of button text when button is larger than text. Defaults to (0.5f, 0.5f) (centered).
     ImVec2      SelectableTextAlign;        // Alignment of selectable text. Defaults to (0.0f, 0.0f) (top-left aligned). It's generally important to keep this left-aligned if you want to lay multiple items on a same line.