Add beginning of cellview as well as improved ViewTypes

This is the beginning of the view refactor (#515). It's just
the start and is untested for now.

cmd/micro/cellview.go

@@ -0,0 +1,108 @@
+package main
+
+import (
+	"github.com/mattn/go-runewidth"
+	"github.com/zyedidia/tcell"
+)
+
+func min(a, b int) int {
+	if a <= b {
+		return a
+	}
+	return b
+}
+
+func VisualToCharPos(visualIndex int, str string, tabsize int) int {
+	visualPos := 0
+	charPos := 0
+	for _, c := range str {
+		width := StringWidth(string(c), tabsize)
+
+		if visualPos+width > visualIndex {
+			return charPos
+		}
+
+		visualPos += width
+		charPos++
+	}
+
+	return 0
+}
+
+type Char struct {
+	visualLoc Loc
+	realLoc   Loc
+	char      rune
+	style     tcell.Style
+}
+
+type CellView struct {
+	lines [][]*Char
+}
+
+func (c *CellView) Draw(buf *Buffer, start, top, height, left, width int) {
+	tabsize := buf.Settings["tabsize"].(int)
+	softwrap := buf.Settings["softwrap"].(bool)
+	indentchar := []rune(buf.Settings["indentchar"].(string))[0]
+
+	if len(c.lines) != height {
+		c.lines = make([][]*Char, height)
+	}
+
+	viewLine := 0
+	lineN := top
+
+	for viewLine < height {
+		lineStr := string(buf.lines[lineN])
+		line := []rune(lineStr)
+
+		colN := VisualToCharPos(left, lineStr, tabsize)
+		viewCol := 0
+
+		// We'll either draw the length of the line, or the width of the screen
+		// whichever is smaller
+		lineLength := min(len(line), width)
+		if len(c.lines[viewLine]) != lineLength {
+			c.lines[viewLine] = make([]*Char, lineLength)
+		}
+
+		wrap := false
+		// We only need to wrap if the length of the line is greater than the width of the terminal screen
+		if softwrap && len(line) > width {
+			wrap = true
+			// We're going to draw the entire line now
+			lineLength = len(line)
+		}
+
+		for viewCol < lineLength {
+			char := line[colN]
+
+			colN++
+			if char == '\t' {
+				c.lines[viewLine][viewCol] = &Char{Loc{viewCol, viewLine}, Loc{colN, lineN}, indentchar, tcell.StyleDefault}
+				// TODO: this always adds 4 spaces but it should really add just the remainder to the next tab location
+				viewCol += tabsize
+			} else if runewidth.RuneWidth(char) > 1 {
+				c.lines[viewLine][viewCol] = &Char{Loc{viewCol, viewLine}, Loc{colN, lineN}, char, tcell.StyleDefault}
+				viewCol += runewidth.RuneWidth(char)
+			} else {
+				c.lines[viewLine][viewCol] = &Char{Loc{viewCol, viewLine}, Loc{colN, lineN}, char, tcell.StyleDefault}
+				viewCol++
+			}
+
+			if wrap && viewCol > width {
+				viewLine++
+				viewCol = 0
+
+				// If we go too far soft wrapping we have to cut off
+				if viewLine >= height {
+					break
+				}
+			}
+		}
+
+		// newline
+		viewLine++
+		lineN++
+	}
+}

cmd/micro/view.go

@@ -11,12 +11,16 @@ import (
 	"github.com/zyedidia/tcell"
 )
 
-type ViewType int
+type ViewType struct {
+	readonly bool // The file cannot be edited
+	scratch  bool // The file cannot be saved
+}
 
-const (
-	vtDefault ViewType = iota
-	vtHelp
-	vtLog
+var (
+	vtDefault = ViewType{false, false}
+	vtHelp    = ViewType{true, true}
+	vtLog     = ViewType{true, true}
+	vtScratch = ViewType{false, true}
 )
 
 // The View struct stores information about a view into a buffer.