From 37cebbc817f587697f876c941427fc6c4a7673ed Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Tue, 7 Mar 2023 07:20:46 +0530
Subject: [PATCH] Implement decoding of mouse events in Go

---
 tools/tui/loop/api.go   |   3 ++
 tools/tui/loop/mouse.go | 109 ++++++++++++++++++++++++++++++++++++++++
 tools/tui/loop/run.go   |  14 ++++++
 3 files changed, 126 insertions(+)
 create mode 100644 tools/tui/loop/mouse.go

diff --git a/tools/tui/loop/api.go b/tools/tui/loop/api.go
index ce83f83ea..f80a53d7e 100644
--- a/tools/tui/loop/api.go
+++ b/tools/tui/loop/api.go
@@ -74,6 +74,9 @@ type Loop struct {
 	// Called when a key event happens
 	OnKeyEvent func(event *KeyEvent) error
 
+	// Called when a mouse event happens
+	OnMouseEvent func(event *MouseEvent) error
+
 	// Called when text is received either from a key event or directly from the terminal
 	// Called with an empty string when bracketed paste ends
 	OnText func(text string, from_key_event bool, in_bracketed_paste bool) error
diff --git a/tools/tui/loop/mouse.go b/tools/tui/loop/mouse.go
new file mode 100644
index 000000000..b927cb3d3
--- /dev/null
+++ b/tools/tui/loop/mouse.go
@@ -0,0 +1,109 @@
+// License: GPLv3 Copyright: 2023, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package loop
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"kitty/tools/utils"
+)
+
+var _ = fmt.Print
+
+type MouseEventType int
+type MouseButtonFlag int
+
+const (
+	MOUSE_PRESS MouseEventType = iota
+	MOUSE_RELEASE
+	MOUSE_MOVE
+)
+const (
+	SHIFT_INDICATOR  int = 1 << 2
+	ALT_INDICATOR        = 1 << 3
+	CTRL_INDICATOR       = 1 << 4
+	MOTION_INDICATOR     = 1 << 5
+)
+
+const NONE, LEFT, MIDDLE, RIGHT, FOURTH, FIFTH, SIXTH, SEVENTH MouseButtonFlag = 0, 1, 2, 4, 8, 16, 32, 64
+const WHEEL_UP, WHEEL_DOWN, WHEEL_LEFT, WHEEL_RIGHT MouseButtonFlag = -1, -2, -4, -8
+
+var bmap = [...]MouseButtonFlag{LEFT, MIDDLE, RIGHT}
+var ebmap = [...]MouseButtonFlag{FOURTH, FIFTH, SIXTH, SEVENTH}
+var wbmap = [...]MouseButtonFlag{WHEEL_UP, WHEEL_DOWN, WHEEL_LEFT, WHEEL_RIGHT}
+
+type MouseEvent struct {
+	Event_type  MouseEventType
+	Buttons     MouseButtonFlag
+	Mods        KeyModifiers
+	Cell, Pixel struct{ x, y int }
+}
+
+func pixel_to_cell(px, length, cell_length int) int {
+	px = utils.Max(0, utils.Min(px, length-1))
+	return px / cell_length
+}
+
+func decode_sgr_mouse(text string, screen_size ScreenSize) *MouseEvent {
+	parts := strings.Split(text, ";")
+	if len(parts) != 3 {
+		return nil
+	}
+	cb, err := strconv.Atoi(parts[0])
+	if err != nil {
+		return nil
+	}
+	ans := MouseEvent{}
+	ans.Pixel.x, err = strconv.Atoi(parts[1])
+	if err != nil {
+		return nil
+	}
+	if len(parts[2]) < 1 {
+		return nil
+	}
+	ans.Pixel.y, err = strconv.Atoi(parts[2][:len(parts[2])-1])
+	m := parts[2][len(parts[2])-1]
+	if m == 'm' {
+		ans.Event_type = MOUSE_RELEASE
+	} else if cb&MOTION_INDICATOR != 0 {
+		ans.Event_type = MOUSE_MOVE
+	}
+	cb3 := cb & 3
+	if cb >= 128 {
+		ans.Buttons |= ebmap[cb3]
+	} else if cb >= 64 {
+		ans.Buttons |= wbmap[cb3]
+	} else if cb3 < 3 {
+		ans.Buttons |= bmap[cb3]
+	}
+	if cb&SHIFT_INDICATOR != 0 {
+		ans.Mods |= SHIFT
+	}
+	if cb&ALT_INDICATOR != 0 {
+		ans.Mods |= ALT
+	}
+	if cb&CTRL_INDICATOR != 0 {
+		ans.Mods |= CTRL
+	}
+	ans.Cell.x = pixel_to_cell(ans.Pixel.x, int(screen_size.WidthPx), int(screen_size.CellWidth))
+	ans.Cell.y = pixel_to_cell(ans.Pixel.y, int(screen_size.HeightPx), int(screen_size.CellHeight))
+
+	return &ans
+}
+
+func MouseEventFromCSI(csi string, screen_size ScreenSize) *MouseEvent {
+	if len(csi) == 0 {
+		return nil
+	}
+	last_char := csi[len(csi)-1]
+	if last_char != 'm' && last_char != 'M' {
+		return nil
+	}
+	csi = csi[:len(csi)-1]
+	if !strings.HasPrefix(csi, "<") {
+		return nil
+	}
+	return decode_sgr_mouse(csi[1:], screen_size)
+}
diff --git a/tools/tui/loop/run.go b/tools/tui/loop/run.go
index 4832c4f07..87624d353 100644
--- a/tools/tui/loop/run.go
+++ b/tools/tui/loop/run.go
@@ -73,12 +73,26 @@ func (self *Loop) handle_csi(raw []byte) error {
 	if ke != nil {
 		return self.handle_key_event(ke)
 	}
+	sz, err := self.ScreenSize()
+	if err == nil {
+		me := MouseEventFromCSI(csi, sz)
+		if me != nil {
+			return self.handle_mouse_event(me)
+		}
+	}
 	if self.OnEscapeCode != nil {
 		return self.OnEscapeCode(CSI, raw)
 	}
 	return nil
 }
 
+func (self *Loop) handle_mouse_event(ev *MouseEvent) error {
+	if self.OnMouseEvent != nil {
+		return self.OnMouseEvent(ev)
+	}
+	return nil
+}
+
 func (self *Loop) handle_key_event(ev *KeyEvent) error {
 	if self.OnKeyEvent != nil {
 		err := self.OnKeyEvent(ev)