Improve scrolling by performing styling in methods called before drawing instead of inside drawing

which then caused the drawing to be abandoned, and black blocks to appear on-screen.
Discard responsive scrolling overdraw when that overdrawn content is invalid.
Style just the visible area instead of the whole document when styling changes run beyond
painting area.

2 files changed, 19 insertions, 3 deletions

diff --git a/src/Editor.cxx b/src/Editor.cxx
index 6c29e7100..6381f7eab 100644
--- a/src/Editor.cxx
+++ b/src/Editor.cxx
@@ -386,6 +386,10 @@ PRectangle Editor::GetClientRectangle() {
 	return wMain.GetClientPosition();
 }
 
+PRectangle Editor::GetClientDrawingRectangle() {
+	return GetClientRectangle();
+}
+
 PRectangle Editor::GetTextRectangle() {
 	PRectangle rc = GetClientRectangle();
 	rc.left += vs.textStart;
@@ -649,6 +653,10 @@ void Editor::RedrawRect(PRectangle rc) {
 	}
 }
 
+void Editor::DiscardOverdraw() {
+	// Overridden on platforms that may draw outside visible area.
+}
+
 void Editor::Redraw() {
 	//Platform::DebugPrintf("Redraw all\n");
 	PRectangle rcClient = GetClientRectangle();
@@ -659,7 +667,10 @@ void Editor::Redraw() {
 }
 
 void Editor::RedrawSelMargin(int line, bool allAfter) {
-	if (!AbandonPaint()) {
+	bool abandonDraw = false;
+	if (!wMargin.GetID())	// Margin in main window so may need to abandon and retry
+		abandonDraw = AbandonPaint();
+	if (!abandonDraw) {
 		if (vs.maskInLine) {
 			Redraw();
 		} else {
@@ -6780,7 +6791,7 @@ int Editor::PositionAfterArea(PRectangle rcArea) const {
 	// The start of the document line after the display line after the area
 	// This often means that the line after a modification is restyled which helps
 	// detect multiline comment additions and heals single line comments
-	int lineAfter = topLine + (rcArea.bottom - 1) / vs.lineHeight + 1;
+	int lineAfter = TopLineOfMain() + (rcArea.bottom - 1) / vs.lineHeight + 1;
 	if (lineAfter < cs.LinesDisplayed())
 		return pdoc->LineStart(cs.DocFromDisplay(lineAfter) + 1);
 	else
@@ -6790,7 +6801,7 @@ int Editor::PositionAfterArea(PRectangle rcArea) const {
 // Style to a position within the view. If this causes a change at end of last line then
 // affects later lines so style all the viewed text.
 void Editor::StyleToPositionInView(Position pos) {
-	int endWindow = (vs.marginInside) ? (PositionAfterArea(GetClientRectangle())) : (pdoc->Length());
+	int endWindow = PositionAfterArea(GetClientDrawingRectangle());
 	if (pos > endWindow)
 		pos = endWindow;
 	int styleAtEnd = pdoc->StyleAt(pos-1);
@@ -6798,6 +6809,9 @@ void Editor::StyleToPositionInView(Position pos) {
 	if ((endWindow > pos) && (styleAtEnd != pdoc->StyleAt(pos-1))) {
 		// Style at end of line changed so is multi-line change like starting a comment
 		// so require rest of window to be styled.
+		DiscardOverdraw();	// Prepared bitmaps may be invalid
+		// DiscardOverdraw may have truncated client drawing area so recalculate endWindow
+		endWindow = PositionAfterArea(GetClientDrawingRectangle());
 		pdoc->EnsureStyledTo(endWindow);
 	}
 }
diff --git a/src/Editor.h b/src/Editor.h
index 588967d64..810175b58 100644
--- a/src/Editor.h
+++ b/src/Editor.h
@@ -338,6 +338,7 @@ protected:	// ScintillaBase subclass needs access to much of Editor
 	Point DocumentPointFromView(Point ptView);  // Convert a point from view space to document
 	int TopLineOfMain() const;   // Return the line at Main's y coordinate 0
 	virtual PRectangle GetClientRectangle();
+	virtual PRectangle GetClientDrawingRectangle();
 	PRectangle GetTextRectangle();
 
 	int LinesOnScreen();
@@ -357,6 +358,7 @@ protected:	// ScintillaBase subclass needs access to much of Editor
 
 	bool AbandonPaint();
 	virtual void RedrawRect(PRectangle rc);
+	virtual void DiscardOverdraw();
 	virtual void Redraw();
 	void RedrawSelMargin(int line=-1, bool allAfter=false);
 	PRectangle RectangleFromRange(int start, int end);