Make the mouse selection code re-useable

tools/tui/mouse.go

@@ -0,0 +1,93 @@
+// License: GPLv3 Copyright: 2023, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package tui
+
+import (
+	"fmt"
+	"kitty/tools/tty"
+	"kitty/tools/tui/loop"
+	"kitty/tools/utils"
+)
+
+var _ = fmt.Print
+
+type LinePos interface {
+	LessThan(other LinePos) bool
+	Equal(other LinePos) bool
+}
+
+type SelectionBoundary struct {
+	line                  LinePos
+	x                     int
+	in_first_half_of_cell bool
+}
+
+func (self *SelectionBoundary) Equal(other SelectionBoundary) bool {
+	if self.x != other.x || self.in_first_half_of_cell != other.in_first_half_of_cell {
+		return false
+	}
+	if self.line == nil {
+		return other.line == nil
+	}
+	return self.line.Equal(other.line)
+}
+
+type MouseSelection struct {
+	start, end              SelectionBoundary
+	is_active               bool
+	min_x, max_x            int
+	min_y, max_y            int
+	cell_width, cell_height int
+}
+
+func (self *MouseSelection) IsEmpty() bool  { return self.start.Equal(self.end) }
+func (self *MouseSelection) IsActive() bool { return self.is_active }
+func (self *MouseSelection) Finish()        { self.is_active = false }
+func (self *MouseSelection) Clear()         { *self = MouseSelection{} }
+
+func (ms *MouseSelection) StartNewSelection(ev *loop.MouseEvent, line LinePos, min_x, max_x, min_y, max_y, cell_width, cell_height int) {
+	*ms = MouseSelection{min_x: min_x, max_x: max_x, cell_width: cell_width, cell_height: cell_height, min_y: min_y, max_y: max_y}
+	ms.start.line = line
+	ms.start.x = utils.Max(ms.min_x, utils.Min(ev.Cell.X, ms.max_x))
+	cell_start := cell_width * ev.Cell.X
+	ms.start.in_first_half_of_cell = ev.Pixel.X <= cell_start+cell_width/2
+	ms.end = ms.start
+	ms.is_active = true
+}
+
+func (ms *MouseSelection) Update(ev *loop.MouseEvent, line LinePos) {
+	if ms.is_active {
+		ms.end.x = utils.Max(ms.min_x, utils.Min(ev.Cell.X, ms.max_x))
+		cell_start := ms.cell_width * ms.end.x
+		ms.end.in_first_half_of_cell = ev.Pixel.X <= cell_start+ms.cell_width/2
+		ms.end.line = line
+	}
+}
+
+var DebugPrintln = tty.DebugPrintln
+
+func (ms *MouseSelection) LineBounds(line_pos LinePos) (start_x, end_x int) {
+	if ms.IsEmpty() {
+		return -1, -1
+	}
+	a, b := ms.start.line, ms.end.line
+	ax, bx := ms.start.x, ms.end.x
+	if b.LessThan(a) {
+		a, b = b, a
+		ax, bx = bx, ax
+	}
+	if a.LessThan(line_pos) {
+		if line_pos.LessThan(b) {
+			return ms.min_x, ms.max_x
+		} else if b.Equal(line_pos) {
+			return ms.min_x, bx
+		}
+	} else if a.Equal(line_pos) {
+		if line_pos.LessThan(b) {
+			return ax, ms.max_x
+		} else if b.Equal(line_pos) {
+			return ax, bx
+		}
+	}
+	return -1, -1
+}