implemented 'area scrolling' (#202)

* implemented 'area scrolling'

* bug fix: area scroll down boundary check

* bug fix: ReverseIndex activates scroll down correctly

buffer/buffer.go

@@ -326,10 +326,6 @@ func (buffer *Buffer) IsDirty() bool {
 	return true
 }
 
-func (buffer *Buffer) GetScrollOffset() uint {
-	return buffer.terminalState.scrollLinesFromBottom
-}
-
 func (buffer *Buffer) HasScrollableRegion() bool {
 	return buffer.terminalState.topMargin > 0 || buffer.terminalState.bottomMargin < uint(buffer.ViewHeight())-1
 }
@@ -338,46 +334,48 @@ func (buffer *Buffer) InScrollableRegion() bool {
 	return buffer.HasScrollableRegion() && uint(buffer.terminalState.cursorY) >= buffer.terminalState.topMargin && uint(buffer.terminalState.cursorY) <= buffer.terminalState.bottomMargin
 }
 
-func (buffer *Buffer) ScrollDown(lines uint16) {
+// NOTE: bottom is exclusive
+func (buffer *Buffer) getAreaScrollRange() (top uint64, bottom uint64) {
+	top = buffer.convertViewLineToRawLine(uint16(buffer.terminalState.topMargin))
+	bottom = buffer.convertViewLineToRawLine(uint16(buffer.terminalState.bottomMargin)) + 1
+	if bottom > uint64(len(buffer.lines)) {
+		bottom = uint64(len(buffer.lines))
+	}
+	return top, bottom
+}
 
+func (buffer *Buffer) AreaScrollDown(lines uint16) {
 	defer buffer.emitDisplayChange()
 
-	if buffer.Height() < int(buffer.ViewHeight()) {
+	// NOTE: bottom is exclusive
-		return
+	top, bottom := buffer.getAreaScrollRange()
-	}
 
-	if uint(lines) > buffer.terminalState.scrollLinesFromBottom {
+	for i := bottom; i > top; {
-		lines = uint16(buffer.terminalState.scrollLinesFromBottom)
+		i--
+		if i >= top+uint64(lines) {
+			buffer.lines[i] = buffer.lines[i-uint64(lines)]
+		} else {
+			buffer.lines[i] = newLine()
+		}
 	}
-	buffer.terminalState.scrollLinesFromBottom -= uint(lines)
 }
 
-func (buffer *Buffer) ScrollUp(lines uint16) {
+func (buffer *Buffer) AreaScrollUp(lines uint16) {
-
 	defer buffer.emitDisplayChange()
 
-	if buffer.Height() < int(buffer.ViewHeight()) {
+	// NOTE: bottom is exclusive
-		return
+	top, bottom := buffer.getAreaScrollRange()
-	}
 
-	if uint(lines)+buffer.terminalState.scrollLinesFromBottom >= (uint(buffer.Height()) - uint(buffer.ViewHeight())) {
+	for i := top; i < bottom; i++ {
-		buffer.terminalState.scrollLinesFromBottom = uint(buffer.Height()) - uint(buffer.ViewHeight())
+		from := i + uint64(lines)
-	} else {
+		if from < bottom {
-		buffer.terminalState.scrollLinesFromBottom += uint(lines)
+			buffer.lines[i] = buffer.lines[from]
+		} else {
+			buffer.lines[i] = newLine()
+		}
 	}
 }
 
-func (buffer *Buffer) ScrollPageDown() {
-	buffer.ScrollDown(buffer.terminalState.viewHeight)
-}
-func (buffer *Buffer) ScrollPageUp() {
-	buffer.ScrollUp(buffer.terminalState.viewHeight)
-}
-func (buffer *Buffer) ScrollToEnd() {
-	defer buffer.emitDisplayChange()
-	buffer.terminalState.scrollLinesFromBottom = 0
-}
-
 func (buffer *Buffer) SaveCursor() {
 	copiedAttr := buffer.terminalState.CursorAttr
 	buffer.savedCursorAttr = &copiedAttr
@@ -595,15 +593,7 @@ func (buffer *Buffer) Index() {
 		if uint(buffer.terminalState.cursorY) < buffer.terminalState.bottomMargin {
 			buffer.terminalState.cursorY++
 		} else {
-
+			buffer.AreaScrollUp(1)
-			topIndex := buffer.convertViewLineToRawLine(uint16(buffer.terminalState.topMargin))
-			bottomIndex := buffer.convertViewLineToRawLine(uint16(buffer.terminalState.bottomMargin))
-
-			for i := topIndex; i < bottomIndex; i++ {
-				buffer.lines[i] = buffer.lines[i+1]
-			}
-
-			buffer.lines[bottomIndex] = newLine()
 		}
 
 		return
@@ -625,25 +615,9 @@ func (buffer *Buffer) ReverseIndex() {
 
 	defer buffer.emitDisplayChange()
 
-	if buffer.InScrollableRegion() {
+	if uint(buffer.terminalState.cursorY) == buffer.terminalState.topMargin {
-
+		buffer.AreaScrollDown(1)
-		if uint(buffer.terminalState.cursorY) > buffer.terminalState.topMargin {
+	} else if buffer.terminalState.cursorY > 0 {
-			buffer.terminalState.cursorY--
-		} else {
-
-			topIndex := buffer.convertViewLineToRawLine(uint16(buffer.terminalState.topMargin))
-			bottomIndex := buffer.convertViewLineToRawLine(uint16(buffer.terminalState.bottomMargin))
-
-			for i := bottomIndex; i > topIndex; i-- {
-				buffer.lines[i] = buffer.lines[i-1]
-			}
-
-			buffer.lines[topIndex] = newLine()
-		}
-		return
-	}
-
-	if buffer.terminalState.cursorY > 0 {
 		buffer.terminalState.cursorY--
 	}
 }

buffer/terminal_state.go

@@ -110,3 +110,15 @@ func (terminalState *TerminalState) TabReset() {
 		i += TabStep
 	}
 }
+
+func (terminalState *TerminalState) ViewHeight() uint16 {
+	return terminalState.viewHeight
+}
+
+func (terminalState *TerminalState) GetScrollOffset() uint {
+	return terminalState.scrollLinesFromBottom
+}
+
+func (terminalState *TerminalState) SetScrollOffset(offset uint) {
+	terminalState.scrollLinesFromBottom = offset
+}

gui/mouse.go

@@ -13,9 +13,9 @@ import (
 func (gui *GUI) glfwScrollCallback(w *glfw.Window, xoff float64, yoff float64) {
 
 	if yoff > 0 {
-		gui.terminal.ScrollUp(1)
+		gui.terminal.ScreenScrollUp(1)
 	} else {
-		gui.terminal.ScrollDown(1)
+		gui.terminal.ScreenScrollDown(1)
 	}
 }
 

terminal/csi.go

@@ -299,7 +299,7 @@ func csiScrollUpHandler(params []string, terminal *Terminal) error {
 		}
 	}
 	terminal.logger.Debugf("Scrolling up %d", distance)
-	terminal.ScrollUp(uint16(distance))
+	terminal.AreaScrollUp(uint16(distance))
 	return nil
 }
 
@@ -370,7 +370,7 @@ func csiScrollDownHandler(params []string, terminal *Terminal) error {
 		}
 	}
 	terminal.logger.Debugf("Scrolling down %d", distance)
-	terminal.ScrollDown(uint16(distance))
+	terminal.AreaScrollDown(uint16(distance))
 	return nil
 }
 

terminal/scr_state.go

@@ -9,7 +9,7 @@ func screenStateHandler(pty chan rune, terminal *Terminal) error {
 		// hide cursor?
 		buffer := terminal.ActiveBuffer()
 		terminal.ResetVerticalMargins()
-		buffer.ScrollToEnd()
+		terminal.ScrollToEnd()
 
 		// Fill the whole screen with E's
 		count := buffer.ViewHeight() * buffer.ViewWidth()

terminal/terminal.go

@@ -154,12 +154,22 @@ func (terminal *Terminal) UsingMainBuffer() bool {
 }
 
 func (terminal *Terminal) GetScrollOffset() uint {
-	return terminal.ActiveBuffer().GetScrollOffset()
+	return terminal.terminalState.GetScrollOffset()
 }
 
-func (terminal *Terminal) ScrollDown(lines uint16) {
+func (terminal *Terminal) ScreenScrollDown(lines uint16) {
-	terminal.ActiveBuffer().ScrollDown(lines)
+	defer terminal.SetDirty()
+	buffer := terminal.ActiveBuffer()
 
+	if buffer.Height() < int(buffer.ViewHeight()) {
+		return
+	}
+
+	offset := terminal.terminalState.GetScrollOffset()
+	if uint(lines) > offset {
+		lines = uint16(offset)
+	}
+	terminal.terminalState.SetScrollOffset(offset - uint(lines))
 }
 
 func (terminal *Terminal) SetCharSize(w float32, h float32) {
@@ -167,18 +177,41 @@ func (terminal *Terminal) SetCharSize(w float32, h float32) {
 	terminal.charHeight = h
 }
 
-func (terminal *Terminal) ScrollUp(lines uint16) {
+func (terminal *Terminal) AreaScrollUp(lines uint16) {
-	terminal.ActiveBuffer().ScrollUp(lines)
+	terminal.ActiveBuffer().AreaScrollUp(lines)
+}
+
+func (terminal *Terminal) AreaScrollDown(lines uint16) {
+	terminal.ActiveBuffer().AreaScrollDown(lines)
+}
+
+func (terminal *Terminal) ScreenScrollUp(lines uint16) {
+	defer terminal.SetDirty()
+	buffer := terminal.ActiveBuffer()
+
+	if buffer.Height() < int(buffer.ViewHeight()) {
+		return
+	}
+
+	offset := terminal.terminalState.GetScrollOffset()
+
+	if uint(lines)+offset >= (uint(buffer.Height()) - uint(buffer.ViewHeight())) {
+		terminal.terminalState.SetScrollOffset(uint(buffer.Height()) - uint(buffer.ViewHeight()))
+	} else {
+		terminal.terminalState.SetScrollOffset(offset + uint(lines))
+	}
 }
 
 func (terminal *Terminal) ScrollPageDown() {
-	terminal.ActiveBuffer().ScrollPageDown()
+	terminal.ScreenScrollDown(terminal.terminalState.ViewHeight())
 }
 func (terminal *Terminal) ScrollPageUp() {
-	terminal.ActiveBuffer().ScrollPageUp()
+	terminal.ScreenScrollUp(terminal.terminalState.ViewHeight())
 }
+
 func (terminal *Terminal) ScrollToEnd() {
-	terminal.ActiveBuffer().ScrollToEnd()
+	defer terminal.SetDirty()
+	terminal.terminalState.SetScrollOffset(0)
 }
 
 func (terminal *Terminal) GetVisibleLines() []buffer.Line {