Fix softwrap scrolling issues (#1981)

Softwrap implementation enhanced to fix various issues with scrolling,
centering, relocating etc.

The main idea is simple: work not with simple line numbers but
with (Line, Row) pairs, where Line is a line number in the buffer
and Row is a visual line (a row) number within this line.
The logic remains mostly the same, but simple arithmetic operations
on line numbers are replaced with corresponding operations on
(Line, Row) pairs.

Fixes #632, #1657

internal/action/actions.go

@@ -10,6 +10,7 @@ import (
 	"github.com/zyedidia/micro/v2/internal/buffer"
 	"github.com/zyedidia/micro/v2/internal/clipboard"
 	"github.com/zyedidia/micro/v2/internal/config"
+	"github.com/zyedidia/micro/v2/internal/display"
 	"github.com/zyedidia/micro/v2/internal/screen"
 	"github.com/zyedidia/micro/v2/internal/shell"
 	"github.com/zyedidia/micro/v2/internal/util"
@@ -19,21 +20,26 @@ import (
 // ScrollUp is not an action
 func (h *BufPane) ScrollUp(n int) {
 	v := h.GetView()
-	if v.StartLine >= n {
-		v.StartLine -= n
-		h.SetView(v)
-	} else {
-		v.StartLine = 0
-	}
+	v.StartLine = h.Scroll(v.StartLine, -n)
+	h.SetView(v)
 }
 
 // ScrollDown is not an action
 func (h *BufPane) ScrollDown(n int) {
 	v := h.GetView()
-	if v.StartLine <= h.Buf.LinesNum()-1-n {
-		v.StartLine += n
-		h.SetView(v)
+	v.StartLine = h.Scroll(v.StartLine, n)
+	h.SetView(v)
+}
+
+// If the user has scrolled past the last line, ScrollAdjust can be used
+// to shift the view so that the last line is at the bottom
+func (h *BufPane) ScrollAdjust() {
+	v := h.GetView()
+	end := h.SLocFromLoc(h.Buf.End())
+	if h.Diff(v.StartLine, end) < v.Height-1 {
+		v.StartLine = h.Scroll(end, -v.Height+1)
 	}
+	h.SetView(v)
 }
 
 // MousePress is the event that should happen when a normal click happens
@@ -111,15 +117,9 @@ func (h *BufPane) ScrollDownAction() bool {
 // Center centers the view on the cursor
 func (h *BufPane) Center() bool {
 	v := h.GetView()
-	v.StartLine = h.Cursor.Y - v.Height/2
-	if v.StartLine+v.Height > h.Buf.LinesNum() {
-		v.StartLine = h.Buf.LinesNum() - v.Height
-	}
-	if v.StartLine < 0 {
-		v.StartLine = 0
-	}
+	v.StartLine = h.Scroll(h.SLocFromLoc(h.Cursor.Loc), -v.Height/2)
 	h.SetView(v)
-	h.Relocate()
+	h.ScrollAdjust()
 	return true
 }
 
@@ -1243,45 +1243,31 @@ func (h *BufPane) JumpLine() bool {
 // Start moves the viewport to the start of the buffer
 func (h *BufPane) Start() bool {
 	v := h.GetView()
-	v.StartLine = 0
+	v.StartLine = display.SLoc{0, 0}
 	h.SetView(v)
 	return true
 }
 
 // End moves the viewport to the end of the buffer
 func (h *BufPane) End() bool {
-	// TODO: softwrap problems?
 	v := h.GetView()
-	if v.Height > h.Buf.LinesNum() {
-		v.StartLine = 0
-		h.SetView(v)
-	} else {
-		v.StartLine = h.Buf.LinesNum() - v.Height
-		h.SetView(v)
-	}
+	v.StartLine = h.Scroll(h.SLocFromLoc(h.Buf.End()), -v.Height+1)
+	h.SetView(v)
 	return true
 }
 
 // PageUp scrolls the view up a page
 func (h *BufPane) PageUp() bool {
 	v := h.GetView()
-	if v.StartLine > v.Height {
-		h.ScrollUp(v.Height)
-	} else {
-		v.StartLine = 0
-	}
-	h.SetView(v)
+	h.ScrollUp(v.Height)
 	return true
 }
 
 // PageDown scrolls the view down a page
 func (h *BufPane) PageDown() bool {
 	v := h.GetView()
-	if h.Buf.LinesNum()-(v.StartLine+v.Height) > v.Height {
-		h.ScrollDown(v.Height)
-	} else if h.Buf.LinesNum() >= v.Height {
-		v.StartLine = h.Buf.LinesNum() - v.Height
-	}
+	h.ScrollDown(v.Height)
+	h.ScrollAdjust()
 	return true
 }
 
@@ -1338,24 +1324,15 @@ func (h *BufPane) CursorPageDown() bool {
 // HalfPageUp scrolls the view up half a page
 func (h *BufPane) HalfPageUp() bool {
 	v := h.GetView()
-	if v.StartLine > v.Height/2 {
-		h.ScrollUp(v.Height / 2)
-	} else {
-		v.StartLine = 0
-	}
-	h.SetView(v)
+	h.ScrollUp(v.Height / 2)
 	return true
 }
 
 // HalfPageDown scrolls the view down half a page
 func (h *BufPane) HalfPageDown() bool {
 	v := h.GetView()
-	if h.Buf.LinesNum()-(v.StartLine+v.Height) > v.Height/2 {
-		h.ScrollDown(v.Height / 2)
-	} else if h.Buf.LinesNum() >= v.Height {
-		v.StartLine = h.Buf.LinesNum() - v.Height
-	}
-	h.SetView(v)
+	h.ScrollDown(v.Height / 2)
+	h.ScrollAdjust()
 	return true
 }
 

internal/action/globals.go

@@ -21,13 +21,6 @@ func WriteLog(s string) {
 	buffer.WriteLog(s)
 	if LogBufPane != nil {
 		LogBufPane.CursorEnd()
-		v := LogBufPane.GetView()
-		endY := buffer.LogBuf.End().Y
-
-		if endY > v.StartLine+v.Height {
-			v.StartLine = buffer.LogBuf.End().Y - v.Height + 2
-			LogBufPane.SetView(v)
-		}
 	}
 }
 
@@ -37,12 +30,4 @@ func WriteLog(s string) {
 func (h *BufPane) OpenLogBuf() {
 	LogBufPane = h.HSplitBuf(buffer.LogBuf)
 	LogBufPane.CursorEnd()
-
-	v := LogBufPane.GetView()
-	endY := buffer.LogBuf.End().Y
-
-	if endY > v.StartLine+v.Height {
-		v.StartLine = buffer.LogBuf.End().Y - v.Height + 2
-		LogBufPane.SetView(v)
-	}
 }