Clamping column offset in text view.

textview.go

@@ -22,7 +22,7 @@ var textColors = map[string]tcell.Color{
 
 // Regular expressions commonly used throughout the TextView class.
 var (
-	colorPattern  = regexp.MustCompile(`\[(white|yellow|blue|green|red)\]`)
+	colorPattern  *regexp.Regexp // Initialized in the init() function.
 	regionPattern = regexp.MustCompile(`\["([a-zA-Z0-9_,;: \-\.]*)"\]`)
 )
 
@@ -54,7 +54,8 @@ type textViewIndex struct {
 //   - Ctrl-F, page down: Move down by one page.
 //   - Ctrl-B, page up: Move up by one page.
 //
-// If the text is not scrollable, any text above the top line is discarded.
+// If the text is not scrollable, any text above the top visible line is
+// discarded.
 //
 // Navigation can be intercepted by installing a callback function via
 // SetCaptureFunc() which receives all keyboard events and decides which ones
@@ -116,6 +117,9 @@ type TextView struct {
 	// The display width for which the index is created.
 	indexWidth int
 
+	// The width of the longest line in the index (not the buffer).
+	longestLine int
+
 	// The index of the first line shown in the text view.
 	lineOffset int
 
@@ -435,6 +439,7 @@ func (t *TextView) reindexBuffer(width int) {
 		regionID    string
 		highlighted bool
 	)
+	t.longestLine = 0
 	color := t.textColor
 	if !t.wrap {
 		width = math.MaxInt64
@@ -523,6 +528,11 @@ func (t *TextView) reindexBuffer(width int) {
 			if t.wrap && currentWidth >= width {
 				currentWidth = 0
 			}
+
+			// Do we have a new maximum width?
+			if currentWidth > t.longestLine {
+				t.longestLine = currentWidth
+			}
 		}
 	}
 
@@ -566,6 +576,14 @@ func (t *TextView) Draw(screen tcell.Screen) {
 		t.lineOffset = 0
 	}
 
+	// Adjust column offset.
+	if t.columnOffset+width > t.longestLine {
+		t.columnOffset = t.longestLine - width
+	}
+	if t.columnOffset < 0 {
+		t.columnOffset = 0
+	}
+
 	// Draw the buffer.
 	for line := t.lineOffset; line < len(t.index); line++ {
 		// Are we done?
@@ -695,9 +713,6 @@ func (t *TextView) InputHandler() func(event *tcell.EventKey, setFocus func(p Pr
 				t.lineOffset--
 			case 'h': // Left.
 				t.columnOffset--
-				if t.columnOffset < 0 {
-					t.columnOffset = 0
-				}
 			case 'l': // Right.
 				t.columnOffset++
 			}
@@ -715,9 +730,6 @@ func (t *TextView) InputHandler() func(event *tcell.EventKey, setFocus func(p Pr
 			t.lineOffset++
 		case tcell.KeyLeft:
 			t.columnOffset--
-			if t.columnOffset < 0 {
-				t.columnOffset = 0
-			}
 		case tcell.KeyRight:
 			t.columnOffset++
 		case tcell.KeyPgDn, tcell.KeyCtrlF:

util.go

@@ -2,6 +2,7 @@ package tview
 
 import (
 	"math"
+	"regexp"
 	"strconv"
 	"strings"
 
@@ -53,8 +54,7 @@ var (
 
 // Package initialization.
 func init() {
-	// Initialize the predefined handlers.
-
+	// Initialize the predefined input field handlers.
 	InputFieldInteger = func(text string, ch rune) bool {
 		if text == "-" {
 			return true
@@ -62,7 +62,6 @@ func init() {
 		_, err := strconv.Atoi(text)
 		return err == nil
 	}
-
 	InputFieldFloat = func(text string, ch rune) bool {
 		if text == "-" || text == "." {
 			return true
@@ -70,12 +69,21 @@ func init() {
 		_, err := strconv.ParseFloat(text, 64)
 		return err == nil
 	}
-
 	InputFieldMaxLength = func(maxLength int) func(text string, ch rune) bool {
 		return func(text string, ch rune) bool {
 			return len([]rune(text)) <= maxLength
 		}
 	}
+
+	// Regular expressions.
+	var colors string
+	for color := range textColors {
+		if len(colors) > 0 {
+			colors += "|"
+		}
+		colors += color
+	}
+	colorPattern = regexp.MustCompile(`\[(` + colors + `)\]`)
 }
 
 // Print prints text onto the screen into the given box at (x,y,maxWidth,1),