From 383f3eca40f235e237c3431339cfb6cae007ec17 Mon Sep 17 00:00:00 2001
From: Elias Naur <mail@eliasnaur.com>
Date: Mon, 3 Feb 2020 23:48:20 +0100
Subject: [PATCH] widget: re-layout Editor before processing events if layout
 is invalid

Editor's event processing assumes the cached layout is valid, but
it might not be if the program changed the Editor text between calling
Layout and Events.

Fixes #85 (I think)

Signed-off-by: Elias Naur <mail@eliasnaur.com>
---
 widget/editor.go | 40 ++++++++++++++++++++++++++--------------
 1 file changed, 26 insertions(+), 14 deletions(-)

diff --git a/widget/editor.go b/widget/editor.go
index 4d5505f7..0e41c899 100644
--- a/widget/editor.go
+++ b/widget/editor.go
@@ -35,6 +35,7 @@ type Editor struct {
 
 	eventKey     int
 	font         text.Font
+	shaper       text.Shaper
 	textSize     fixed.Int26_6
 	blinkStart   time.Time
 	focused      bool
@@ -97,10 +98,22 @@ func (e *Editor) Events(gtx *layout.Context) []EditorEvent {
 }
 
 func (e *Editor) processEvents(gtx *layout.Context) {
+	if e.shaper == nil {
+		// Can't process events without a shaper.
+		return
+	}
+	e.makeValid()
 	e.processPointer(gtx)
 	e.processKey(gtx)
 }
 
+func (e *Editor) makeValid() {
+	if !e.valid {
+		e.lines, e.dims = e.layoutText(e.shaper)
+		e.valid = true
+	}
+}
+
 func (e *Editor) processPointer(gtx *layout.Context) {
 	sbounds := e.scrollBounds()
 	var smin, smax int
@@ -223,14 +236,7 @@ func (e *Editor) Layout(gtx *layout.Context, sh text.Shaper, font text.Font, siz
 		e.font = font
 		e.textSize = textSize
 	}
-	e.processEvents(gtx)
-	e.layout(gtx, sh)
-}
-
-func (e *Editor) layout(gtx *layout.Context, sh text.Shaper) {
-	cs := gtx.Constraints
-
-	maxWidth := cs.Width.Max
+	maxWidth := gtx.Constraints.Width.Max
 	if e.SingleLine {
 		maxWidth = inf
 	}
@@ -238,13 +244,19 @@ func (e *Editor) layout(gtx *layout.Context, sh text.Shaper) {
 		e.maxWidth = maxWidth
 		e.invalidate()
 	}
-
-	if !e.valid {
-		e.lines, e.dims = e.layoutText(sh)
-		e.valid = true
+	if sh != e.shaper {
+		e.shaper = sh
+		e.invalidate()
 	}
 
-	e.viewSize = cs.Constrain(e.dims.Size)
+	e.processEvents(gtx)
+	e.layout(gtx)
+}
+
+func (e *Editor) layout(gtx *layout.Context) {
+	e.makeValid()
+
+	e.viewSize = gtx.Constraints.Constrain(e.dims.Size)
 	// Adjust scrolling for new viewport and layout.
 	e.scrollRel(0, 0)
 
@@ -272,7 +284,7 @@ func (e *Editor) layout(gtx *layout.Context, sh text.Shaper) {
 		if !ok {
 			break
 		}
-		path := sh.Shape(e.font, e.textSize, layout)
+		path := e.shaper.Shape(e.font, e.textSize, layout)
 		e.shapes = append(e.shapes, line{off, path})
 	}