screenshot: fix some region mappings

core/internal/screenshot/region_input.go

@@ -71,6 +71,7 @@ func (r *RegionSelector) setupPointerHandlers() {
 			case 1: // pressed
 				r.selection.hasSelection = true
 				r.selection.dragging = true
+				r.selection.surface = r.activeSurface // Lock to this surface
 				r.selection.anchorX = r.pointerX
 				r.selection.anchorY = r.pointerY
 				r.selection.currentX = r.pointerX
@@ -115,12 +116,17 @@ func (r *RegionSelector) setupKeyboardHandlers() {
 }
 
 func (r *RegionSelector) finishSelection() {
-	if r.activeSurface == nil {
+	if r.selection.surface == nil {
 		r.running = false
 		return
 	}
 
-	os := r.activeSurface
+	os := r.selection.surface
+	srcBuf := r.getSourceBuffer(os)
+	if srcBuf == nil {
+		r.running = false
+		return
+	}
 
 	x1, y1 := r.selection.anchorX, r.selection.anchorY
 	x2, y2 := r.selection.currentX, r.selection.currentY
@@ -133,13 +139,29 @@ func (r *RegionSelector) finishSelection() {
 	}
 
 	scaleX, scaleY := 1.0, 1.0
-	if os.logicalW > 0 && os.screenBuf != nil {
-		scaleX = float64(os.screenBuf.Width) / float64(os.logicalW)
-		scaleY = float64(os.screenBuf.Height) / float64(os.logicalH)
+	if os.logicalW > 0 {
+		scaleX = float64(srcBuf.Width) / float64(os.logicalW)
+		scaleY = float64(srcBuf.Height) / float64(os.logicalH)
 	}
 
-	bx1, by1 := int32(x1*scaleX), int32(y1*scaleY)
-	bx2, by2 := int32(x2*scaleX), int32(y2*scaleY)
+	bx1 := int(x1 * scaleX)
+	by1 := int(y1 * scaleY)
+	bx2 := int(x2 * scaleX)
+	by2 := int(y2 * scaleY)
+
+	// Clamp to buffer bounds
+	if bx1 < 0 {
+		bx1 = 0
+	}
+	if by1 < 0 {
+		by1 = 0
+	}
+	if bx2 > srcBuf.Width {
+		bx2 = srcBuf.Width
+	}
+	if by2 > srcBuf.Height {
+		by2 = srcBuf.Height
+	}
 
 	w, h := bx2-bx1, by2-by1
 	if w < 1 {
@@ -149,11 +171,51 @@ func (r *RegionSelector) finishSelection() {
 		h = 1
 	}
 
+	// Create cropped buffer and copy pixels directly
+	cropped, err := CreateShmBuffer(w, h, w*4)
+	if err != nil {
+		r.running = false
+		return
+	}
+
+	srcData := srcBuf.Data()
+	dstData := cropped.Data()
+	for y := 0; y < h; y++ {
+		srcY := by1 + y
+		if srcY >= srcBuf.Height {
+			break
+		}
+		for x := 0; x < w; x++ {
+			srcX := bx1 + x
+			if srcX >= srcBuf.Width {
+				break
+			}
+			si := srcY*srcBuf.Stride + srcX*4
+			di := y*cropped.Stride + x*4
+			if si+3 < len(srcData) && di+3 < len(dstData) {
+				dstData[di+0] = srcData[si+0]
+				dstData[di+1] = srcData[si+1]
+				dstData[di+2] = srcData[si+2]
+				dstData[di+3] = srcData[si+3]
+			}
+		}
+	}
+
+	r.capturedBuffer = cropped
+	r.capturedRegion = Region{
+		X:      int32(bx1),
+		Y:      int32(by1),
+		Width:  int32(w),
+		Height: int32(h),
+		Output: os.output.name,
+	}
+
+	// Also store for "last region" feature with global coords
 	r.result = Region{
-		X:      bx1 + os.output.x,
-		Y:      by1 + os.output.y,
-		Width:  w,
-		Height: h,
+		X:      int32(bx1) + os.output.x,
+		Y:      int32(by1) + os.output.y,
+		Width:  int32(w),
+		Height: int32(h),
 		Output: os.output.name,
 	}