Display optimisations.

When horizontally scrolled on Windows, an extra message turns up to say the
scrolling has ended. Now has no effect as new scroll position compared to
old and processing only occurs if different.
Avoid working on line segments that are before horizontal visible range.
Guards against working on line segments that are outside visible range
horizontally applied to tabs and control characters as well as text.

1 files changed, 75 insertions, 78 deletions

diff --git a/src/Editor.cxx b/src/Editor.cxx
index 4fa10968d..e852723b2 100644
--- a/src/Editor.cxx
+++ b/src/Editor.cxx
@@ -603,11 +603,13 @@ void Editor::ScrollText(int /* linesToMove */) {
 
 void Editor::HorizontalScrollTo(int xPos) {
 	//Platform::DebugPrintf("HorizontalScroll %d\n", xPos);
-	xOffset = xPos;
-	if (xOffset < 0)
-		xOffset = 0;
-	SetHorizontalScrollPos();
-	RedrawRect(GetClientRectangle());
+	if (xPos < 0)
+		xPos = 0;
+	if (xOffset != xPos) {
+		xOffset = xPos;
+		SetHorizontalScrollPos();
+		RedrawRect(GetClientRectangle());
+	}
 }
 
 void Editor::MoveCaretInsideView() {
@@ -1075,83 +1077,78 @@ void Editor::DrawLine(Surface *surface, ViewStyle &vsDraw, int line, int lineVis
 		        IsControlCharacter(ll.chars[i]) || IsControlCharacter(ll.chars[i + 1]) ||
 		        ((ll.selStart != ll.selEnd) && ((iDoc + 1 == ll.selStart) || (iDoc + 1 == ll.selEnd))) ||
 		        (i == (ll.edgeColumn - 1))) {
-			int styleMain = ll.styles[i];
-			ColourAllocated textBack = vsDraw.styles[styleMain].back.allocated;
-			ColourAllocated textFore = vsDraw.styles[styleMain].fore.allocated;
-			Font &textFont = vsDraw.styles[styleMain].font;
-			bool inSelection = (iDoc >= ll.selStart) && (iDoc < ll.selEnd) && (ll.selStart != ll.selEnd);
-			if (inSelection) {
-				if (vsDraw.selbackset) {
-					if (primarySelection)
-						textBack = vsDraw.selbackground.allocated;
-					else
-						textBack = vsDraw.selbackground2.allocated;
-				}
-				if (vsDraw.selforeset)
-					textFore = vsDraw.selforeground.allocated;
-			} else {
-				if (overrideBackground)
-					textBack = background;
-				if ((vsDraw.edgeState == EDGE_BACKGROUND) && (i >= ll.edgeColumn) && (ll.chars[i] != '\n') && (ll.chars[i] != '\r'))
-					textBack = vsDraw.edgecolour.allocated;
-			}
-			// Manage tab display
-			if (ll.chars[i] == '\t') {
-				rcSegment.left = ll.positions[i] + xStart;
-				rcSegment.right = ll.positions[i + 1] + xStart;
-				surface->FillRectangle(rcSegment, textBack);
-				if ((vsDraw.viewWhitespace != wsInvisible) || ((inIndentation && vsDraw.viewIndentationGuides))) {
-					surface->PenColour(textFore);
+			rcSegment.left = ll.positions[startseg] + xStart;
+			rcSegment.right = ll.positions[i + 1] + xStart;
+			// Only try to draw if really visible - enhances performance by not calling environment to
+			// draw strings that are completely past the right side of the window.
+			//if (rcSegment.left <= rcLine.right) {
+			if ((rcSegment.left <= rcLine.right) && (rcSegment.right >= rcLine.left)) {
+				int styleMain = ll.styles[i];
+				ColourAllocated textBack = vsDraw.styles[styleMain].back.allocated;
+				ColourAllocated textFore = vsDraw.styles[styleMain].fore.allocated;
+				Font &textFont = vsDraw.styles[styleMain].font;
+				bool inSelection = (iDoc >= ll.selStart) && (iDoc < ll.selEnd) && (ll.selStart != ll.selEnd);
+				if (inSelection) {
+					if (vsDraw.selbackset) {
+						if (primarySelection)
+							textBack = vsDraw.selbackground.allocated;
+						else
+							textBack = vsDraw.selbackground2.allocated;
+					}
+					if (vsDraw.selforeset)
+						textFore = vsDraw.selforeground.allocated;
+				} else {
+					if (overrideBackground)
+						textBack = background;
+					if ((vsDraw.edgeState == EDGE_BACKGROUND) && (i >= ll.edgeColumn) && (ll.chars[i] != '\n') && (ll.chars[i] != '\r'))
+						textBack = vsDraw.edgecolour.allocated;
 				}
-				if (inIndentation && vsDraw.viewIndentationGuides) {
-					for (int xIG = ll.positions[i] / indentWidth * indentWidth; xIG < ll.positions[i + 1]; xIG += indentWidth) {
-						if (xIG >= ll.positions[i] && xIG > 0) {
-							Point from(0, ((lineVisible & 1) && (vsDraw.lineHeight & 1)) ? 1 : 0);
-							PRectangle rcCopyArea(xIG + xStart + 1, rcSegment.top, xIG + xStart + 2, rcSegment.bottom);
-							surface->Copy(rcCopyArea, from, (ll.xHighlightGuide == xIG) ?
-							              *pixmapIndentGuideHighlight : *pixmapIndentGuide);
+				if (ll.chars[i] == '\t') {
+					// Manage tab display
+					surface->FillRectangle(rcSegment, textBack);
+					if ((vsDraw.viewWhitespace != wsInvisible) || ((inIndentation && vsDraw.viewIndentationGuides))) {
+						surface->PenColour(textFore);
+					}
+					if (inIndentation && vsDraw.viewIndentationGuides) {
+						for (int xIG = ll.positions[i] / indentWidth * indentWidth; xIG < ll.positions[i + 1]; xIG += indentWidth) {
+							if (xIG >= ll.positions[i] && xIG > 0) {
+								Point from(0, ((lineVisible & 1) && (vsDraw.lineHeight & 1)) ? 1 : 0);
+								PRectangle rcCopyArea(xIG + xStart + 1, rcSegment.top, xIG + xStart + 2, rcSegment.bottom);
+								surface->Copy(rcCopyArea, from, (ll.xHighlightGuide == xIG) ?
+									      *pixmapIndentGuideHighlight : *pixmapIndentGuide);
+							}
 						}
 					}
-				}
-				if (vsDraw.viewWhitespace != wsInvisible) {
-					if (!inIndentation || vsDraw.viewWhitespace == wsVisibleAlways) {
-						PRectangle rcTab(rcSegment.left + 1, rcSegment.top + 4,
-						                 rcSegment.right - 1, rcSegment.bottom - vsDraw.maxDescent);
-						DrawTabArrow(surface, rcTab, rcSegment.top + vsDraw.lineHeight / 2);
+					if (vsDraw.viewWhitespace != wsInvisible) {
+						if (!inIndentation || vsDraw.viewWhitespace == wsVisibleAlways) {
+							PRectangle rcTab(rcSegment.left + 1, rcSegment.top + 4,
+									 rcSegment.right - 1, rcSegment.bottom - vsDraw.maxDescent);
+							DrawTabArrow(surface, rcTab, rcSegment.top + vsDraw.lineHeight / 2);
+						}
 					}
-				}
-				// Manage control character display
-			}
-			else if (IsControlCharacter(ll.chars[i])) {
-				inIndentation = false;
-				const char *ctrlChar = ControlCharacterString(ll.chars[i]);
-				rcSegment.left = ll.positions[i] + xStart;
-				rcSegment.right = ll.positions[i + 1] + xStart;
-				surface->FillRectangle(rcSegment, textBack);
-				int normalCharHeight = surface->Ascent(ctrlCharsFont) -
-				                       surface->InternalLeading(ctrlCharsFont);
-				PRectangle rcCChar = rcSegment;
-				rcCChar.left = rcCChar.left + 1;
-				rcCChar.top = rcSegment.top + vsDraw.maxAscent - normalCharHeight;
-				rcCChar.bottom = rcSegment.top + vsDraw.maxAscent + 1;
-				PRectangle rcCentral = rcCChar;
-				rcCentral.top++;
-				rcCentral.bottom--;
-				surface->FillRectangle(rcCentral, textFore);
-				PRectangle rcChar = rcCChar;
-				rcChar.left++;
-				rcChar.right--;
-				surface->DrawTextClipped(rcChar, ctrlCharsFont,
-				                         rcSegment.top + vsDraw.maxAscent, ctrlChar, strlen(ctrlChar),
-				                         textBack, textFore);
-				// Manage normal display
-			}
-			else {
-				rcSegment.left = ll.positions[startseg] + xStart;
-				rcSegment.right = ll.positions[i + 1] + xStart;
-				// Only try to draw if really visible - enhances performance by not calling environment to
-				// draw strings that are completely past the right side of the window.
-				if (rcSegment.left <= rcLine.right) {
+				} else if (IsControlCharacter(ll.chars[i])) {
+					// Manage control character display
+					inIndentation = false;
+					const char *ctrlChar = ControlCharacterString(ll.chars[i]);
+					surface->FillRectangle(rcSegment, textBack);
+					int normalCharHeight = surface->Ascent(ctrlCharsFont) -
+							       surface->InternalLeading(ctrlCharsFont);
+					PRectangle rcCChar = rcSegment;
+					rcCChar.left = rcCChar.left + 1;
+					rcCChar.top = rcSegment.top + vsDraw.maxAscent - normalCharHeight;
+					rcCChar.bottom = rcSegment.top + vsDraw.maxAscent + 1;
+					PRectangle rcCentral = rcCChar;
+					rcCentral.top++;
+					rcCentral.bottom--;
+					surface->FillRectangle(rcCentral, textFore);
+					PRectangle rcChar = rcCChar;
+					rcChar.left++;
+					rcChar.right--;
+					surface->DrawTextClipped(rcChar, ctrlCharsFont,
+								 rcSegment.top + vsDraw.maxAscent, ctrlChar, strlen(ctrlChar),
+								 textBack, textFore);
+				} else {
+					// Manage normal display
 					surface->DrawTextNoClip(rcSegment, textFont,
 					                  rcSegment.top + vsDraw.maxAscent, ll.chars + startseg,
 					                  i - startseg + 1, textFore, textBack);