Fix rendering of double-column borders

src/terminal.go

@@ -1064,6 +1064,7 @@ func (t *Terminal) resizeWindows(forcePreview bool) {
 	// Reset preview version so that full redraw occurs
 	t.previewed.version = 0
 
+	bw := t.borderWidth
 	switch t.borderShape {
 	case tui.BorderHorizontal:
 		t.border = t.tui.NewWindow(
@@ -1071,7 +1072,7 @@ func (t *Terminal) resizeWindows(forcePreview bool) {
 			false, tui.MakeBorderStyle(tui.BorderHorizontal, t.unicode))
 	case tui.BorderVertical:
 		t.border = t.tui.NewWindow(
-			marginInt[0], marginInt[3]-2, width+4, height,
+			marginInt[0], marginInt[3]-(1+bw), width+(1+bw)*2, height,
 			false, tui.MakeBorderStyle(tui.BorderVertical, t.unicode))
 	case tui.BorderTop:
 		t.border = t.tui.NewWindow(
@@ -1083,15 +1084,15 @@ func (t *Terminal) resizeWindows(forcePreview bool) {
 			false, tui.MakeBorderStyle(tui.BorderBottom, t.unicode))
 	case tui.BorderLeft:
 		t.border = t.tui.NewWindow(
-			marginInt[0], marginInt[3]-2, width+2, height,
+			marginInt[0], marginInt[3]-(1+bw), width+(1+bw), height,
 			false, tui.MakeBorderStyle(tui.BorderLeft, t.unicode))
 	case tui.BorderRight:
 		t.border = t.tui.NewWindow(
-			marginInt[0], marginInt[3], width+2, height,
+			marginInt[0], marginInt[3], width+(1+bw), height,
 			false, tui.MakeBorderStyle(tui.BorderRight, t.unicode))
 	case tui.BorderRounded, tui.BorderSharp, tui.BorderBold, tui.BorderDouble:
 		t.border = t.tui.NewWindow(
-			marginInt[0]-1, marginInt[3]-2, width+4, height+2,
+			marginInt[0]-1, marginInt[3]-(1+bw), width+(1+bw)*2, height+2,
 			false, tui.MakeBorderStyle(t.borderShape, t.unicode))
 	}
 
@@ -1112,7 +1113,6 @@ func (t *Terminal) resizeWindows(forcePreview bool) {
 				return
 			}
 			hasThreshold := previewOpts.threshold > 0 && previewOpts.alternative != nil
-			bw := t.borderWidth
 			createPreviewWindow := func(y int, x int, w int, h int) {
 				pwidth := w
 				pheight := h

src/tui/tcell.go

@@ -695,13 +695,26 @@ func (w *TcellWindow) drawBorder() {
 	hw := runewidth.RuneWidth(w.borderStyle.horizontal)
 	switch shape {
 	case BorderRounded, BorderSharp, BorderBold, BorderDouble, BorderHorizontal, BorderTop:
-		for x := left; x <= right-hw; x += hw {
+		max := right - 2*hw
+		if shape == BorderHorizontal || shape == BorderTop {
+			max = right - hw
+		}
+		// tcell has an issue displaying two overlapping wide runes
+		// e.g.  SetContent(  HH  )
+		//       SetContent(   TR )
+		//       ==================
+		//                 (  HH  ) => TR is ignored
+		for x := left; x <= max; x += hw {
 			_screen.SetContent(x, top, w.borderStyle.horizontal, nil, style)
 		}
 	}
 	switch shape {
 	case BorderRounded, BorderSharp, BorderBold, BorderDouble, BorderHorizontal, BorderBottom:
-		for x := left; x <= right-hw; x += hw {
+		max := right - 2*hw
+		if shape == BorderHorizontal || shape == BorderBottom {
+			max = right - hw
+		}
+		for x := left; x <= max; x += hw {
 			_screen.SetContent(x, bot-1, w.borderStyle.horizontal, nil, style)
 		}
 	}
@@ -713,8 +726,9 @@ func (w *TcellWindow) drawBorder() {
 	}
 	switch shape {
 	case BorderRounded, BorderSharp, BorderBold, BorderDouble, BorderVertical, BorderRight:
+		vw := runewidth.RuneWidth(w.borderStyle.vertical)
 		for y := top; y < bot; y++ {
-			_screen.SetContent(right-hw, y, w.borderStyle.vertical, nil, style)
+			_screen.SetContent(right-vw, y, w.borderStyle.vertical, nil, style)
 		}
 	}
 	switch shape {