Feature [feature-requests:#1582]. Improve performance of Document::SetStyles.

Report changed range for Document::SetStyleFor.

3 files changed, 107 insertions, 45 deletions

diff --git a/src/CellBuffer.cxx b/src/CellBuffer.cxx
index 3e9deb934..3d4050633 100644
--- a/src/CellBuffer.cxx
+++ b/src/CellBuffer.cxx
@@ -439,35 +439,90 @@ const char *CellBuffer::InsertString(Sci::Position position, const char *s, Sci:
 	return data;
 }
 
-bool CellBuffer::SetStyleAt(Sci::Position position, char styleValue) noexcept {
-	if (!hasStyles) {
-		return false;
-	}
-	const char curVal = style.ValueAt(position);
-	if (curVal != styleValue) {
-		style.SetValueAt(position, styleValue);
-		return true;
-	} else {
-		return false;
+namespace {
+
+ChangedRange CopyBytes(char *p, const char *styles, Sci::Position length, Sci::Position offset) noexcept {
+	for (Sci::Position start = 0; start < length; start++) {
+		if (p[start] != styles[start]) {
+			for (Sci::Position end = length - 1; end >= 0; end--) {
+				if (p[end] != styles[end]) {
+					memcpy(p+start, styles+start, end-start+1);
+					return { start + offset, end + offset };
+				}
+			}
+		}
 	}
+	return {};
 }
 
-bool CellBuffer::SetStyleFor(Sci::Position position, Sci::Position lengthStyle, char styleValue) noexcept {
-	if (!hasStyles) {
-		return false;
-	}
-	bool changed = false;
-	PLATFORM_ASSERT(lengthStyle == 0 ||
-		(lengthStyle > 0 && lengthStyle + position <= style.Length()));
-	while (lengthStyle--) {
-		const char curVal = style.ValueAt(position);
-		if (curVal != styleValue) {
-			style.SetValueAt(position, styleValue);
-			changed = true;
+ChangedRange SetBytes(char *p, char style, Sci::Position length, Sci::Position offset) noexcept {
+	for (Sci::Position start = 0; start < length; start++) {
+		if (p[start] != style) {
+			for (Sci::Position end = length - 1; end >= 0; end--) {
+				if (p[end] != style) {
+					memset(p+start, style, end-start+1);
+					return { start + offset, end + offset };
+				}
+			}
 		}
-		position++;
 	}
-	return changed;
+	return {};
+}
+
+struct Lengths {
+	Sci::Position length1;
+	Sci::Position length2;
+};
+
+Lengths SplitUpdate(const SplitVector<char> &style, Sci::Position position, Sci::Position length) noexcept {
+	length = std::min(length, style.Length() - position);
+
+	// Divide length into two parts if it overlaps the gap
+	const Sci::Position part1Length = style.GapPosition();
+
+	// If all after gap then place in length1 to avoid second call
+	if (position >= part1Length) {
+		return { length, 0 };
+	}
+	// If all before gap then place in length1
+	const Sci::Position beforeGap = part1Length - position;
+	if (length <= beforeGap) {
+		return { length, 0 };
+	}
+	// Some before gap and some after gap so put portion in length1 and rest in length2
+	return { beforeGap, length - beforeGap };
+}
+
+}
+
+ChangedRange CellBuffer::SetStyles(Sci::Position position, const char *styles, Sci::Position length) noexcept {
+	if (!hasStyles || (position < 0) || (length <= 0)) {
+		return {};
+	}
+
+	const Lengths lengths = SplitUpdate(style, position, length);
+	ChangedRange cr = CopyBytes(&style[position], styles, lengths.length1, position);
+	if (lengths.length2) {
+		const ChangedRange cr2 = CopyBytes(&style[position + lengths.length1], styles + lengths.length1,
+			lengths.length2, position + lengths.length1);
+		cr.Merge(cr2);
+	}
+	return cr;
+}
+
+ChangedRange CellBuffer::SetStyleFor(Sci::Position position, Sci::Position lengthStyle, char styleValue) noexcept {
+	if (!hasStyles || (position < 0) || (lengthStyle <= 0)) {
+		return {};
+	}
+
+	const Lengths lengths = SplitUpdate(style, position, lengthStyle);
+	ChangedRange cr = SetBytes(&style[position], styleValue, lengths.length1, position);
+	if (lengths.length2) {
+		const ChangedRange cr2 = SetBytes(&style[position + lengths.length1], styleValue,
+			lengths.length2, position + lengths.length1);
+		cr.Merge(cr2);
+	}
+	return cr;
 }
 
 // The char* returned is to an allocation owned by the undo history
diff --git a/src/CellBuffer.h b/src/CellBuffer.h
index 1b035597a..e48eded4d 100644
--- a/src/CellBuffer.h
+++ b/src/CellBuffer.h
@@ -66,6 +66,24 @@ struct SplitView {
 	}
 };
 
+struct ChangedRange {
+	Sci::Position start = Sci::invalidPosition;
+	Sci::Position end = Sci::invalidPosition;
+	ChangedRange() noexcept = default;
+	ChangedRange(Sci::Position start_, Sci::Position end_) noexcept : start(start_), end(end_) {}
+	[[nodiscard]] bool Empty() const noexcept {
+		return start < 0;
+	}
+	void Merge(const ChangedRange &cr2) noexcept {
+		if (cr2.start >= 0) {
+			if (start < 0) {
+				*this = cr2;
+			} else {
+				end = cr2.end;
+			}
+		}
+	}
+};
 
 /**
  * Holder for an expandable array of characters that supports undo and line markers.
@@ -141,9 +159,9 @@ public:
 	const char *InsertString(Sci::Position position, const char *s, Sci::Position insertLength, bool &startSequence);
 
 	/// Setting styles for positions outside the range of the buffer is safe and has no effect.
-	/// @return true if the style of a character is changed.
-	bool SetStyleAt(Sci::Position position, char styleValue) noexcept;
-	bool SetStyleFor(Sci::Position position, Sci::Position lengthStyle, char styleValue) noexcept;
+	/// @return range where style of characters changed.
+	ChangedRange SetStyles(Sci::Position position, const char *styles, Sci::Position length) noexcept;
+	ChangedRange SetStyleFor(Sci::Position position, Sci::Position lengthStyle, char styleValue) noexcept;
 
 	const char *DeleteChars(Sci::Position position, Sci::Position deleteLength, bool &startSequence);
 
diff --git a/src/Document.cxx b/src/Document.cxx
index ab4da0179..d4754233e 100644
--- a/src/Document.cxx
+++ b/src/Document.cxx
@@ -2571,10 +2571,10 @@ bool SCI_METHOD Document::SetStyleFor(Sci_Position length, char style) {
 		return false;
 	}
 	enteredStyling++;
-	const Sci::Position prevEndStyled = endStyled;
-	if (cb.SetStyleFor(endStyled, length, style)) {
+	const ChangedRange cr = cb.SetStyleFor(endStyled, length, style);
+	if (!cr.Empty()) {
 		const DocModification mh(ModificationFlags::ChangeStyle | ModificationFlags::User,
-			                prevEndStyled, length);
+			                cr.start, cr.end - cr.start + 1);
 		NotifyModified(mh);
 	}
 	endStyled += length;
@@ -2587,22 +2587,11 @@ bool SCI_METHOD Document::SetStyles(Sci_Position length, const char *styles) {
 		return false;
 	}
 	enteredStyling++;
-	bool didChange = false;
-	Sci::Position startMod = 0;
-	Sci::Position endMod = 0;
-	for (int iPos = 0; iPos < length; iPos++, endStyled++) {
-		PLATFORM_ASSERT(endStyled < Length());
-		if (cb.SetStyleAt(endStyled, styles[iPos])) {
-			if (!didChange) {
-				startMod = endStyled;
-			}
-			didChange = true;
-			endMod = endStyled;
-		}
-	}
-	if (didChange) {
+	const ChangedRange cr = cb.SetStyles(endStyled, styles, length);
+	endStyled += length;
+	if (!cr.Empty()) {
 		const DocModification mh(ModificationFlags::ChangeStyle | ModificationFlags::User,
-			                startMod, endMod - startMod + 1);
+			                cr.start, cr.end - cr.start + 1);
 		NotifyModified(mh);
 	}
 	enteredStyling--;