screenshot: add shift to perfect-square capability

core/internal/screenshot/region.go

@@ -85,6 +85,7 @@ type RegionSelector struct {
 	pointerY           float64
 	preSelect          Region
 	showCapturedCursor bool
+	shiftHeld          bool
 
 	running   bool
 	cancelled bool

core/internal/screenshot/region_input.go

@@ -51,13 +51,42 @@ func (r *RegionSelector) setupPointerHandlers() {
 		r.pointerX = e.SurfaceX
 		r.pointerY = e.SurfaceY
 
-		if r.selection.dragging {
-			r.selection.currentX = e.SurfaceX
-			r.selection.currentY = e.SurfaceY
+		if !r.selection.dragging {
+			return
+		}
+
+		curX, curY := e.SurfaceX, e.SurfaceY
+		if r.shiftHeld {
+			dx := curX - r.selection.anchorX
+			dy := curY - r.selection.anchorY
+			adx, ady := dx, dy
+			if adx < 0 {
+				adx = -adx
+			}
+			if ady < 0 {
+				ady = -ady
+			}
+			size := adx
+			if ady > adx {
+				size = ady
+			}
+			if dx < 0 {
+				curX = r.selection.anchorX - size
+			} else {
+				curX = r.selection.anchorX + size
+			}
+			if dy < 0 {
+				curY = r.selection.anchorY - size
+			} else {
+				curY = r.selection.anchorY + size
+			}
+		}
+
+		r.selection.currentX = curX
+		r.selection.currentY = curY
 		for _, os := range r.surfaces {
 			r.redrawSurface(os)
 		}
-		}
 	})
 
 	r.pointer.SetButtonHandler(func(e client.PointerButtonEvent) {
@@ -93,21 +122,25 @@ func (r *RegionSelector) setupPointerHandlers() {
 }
 
 func (r *RegionSelector) setupKeyboardHandlers() {
+	r.keyboard.SetModifiersHandler(func(e client.KeyboardModifiersEvent) {
+		r.shiftHeld = e.ModsDepressed&1 != 0
+	})
+
 	r.keyboard.SetKeyHandler(func(e client.KeyboardKeyEvent) {
 		if e.State != 1 {
 			return
 		}
 
 		switch e.Key {
-		case 1: // KEY_ESC
+		case 1:
 			r.cancelled = true
 			r.running = false
-		case 25: // KEY_P
+		case 25:
 			r.showCapturedCursor = !r.showCapturedCursor
 			for _, os := range r.surfaces {
 				r.redrawSurface(os)
 			}
-		case 28, 57: // KEY_ENTER, KEY_SPACE
+		case 28, 57:
 			if r.selection.hasSelection {
 				r.finishSelection()
 			}
@@ -163,7 +196,14 @@ func (r *RegionSelector) finishSelection() {
 		by2 = srcBuf.Height
 	}
 
-	w, h := bx2-bx1, by2-by1
+	w, h := bx2-bx1+1, by2-by1+1
+	if r.shiftHeld && w != h {
+		if w < h {
+			h = w
+		} else {
+			w = h
+		}
+	}
 	if w < 1 {
 		w = 1
 	}

core/internal/screenshot/region_render.go

@@ -114,6 +114,13 @@ func (r *RegionSelector) drawOverlay(os *OutputSurface, renderBuf *ShmBuffer) {
 	}
 
 	selW, selH := bx2-bx1+1, by2-by1+1
+	if r.shiftHeld && selW != selH {
+		if selW < selH {
+			selH = selW
+		} else {
+			selW = selH
+		}
+	}
 	r.drawBorder(data, stride, w, h, bx1, by1, selW, selH)
 	r.drawDimensions(data, stride, w, h, bx1, by1, selW, selH)
 }