From e20c6d05f8b3a13a0fd222b4835c0b6b61cdb9b9 Mon Sep 17 00:00:00 2001
From: Ayke van Laethem <aykevanlaethem@gmail.com>
Date: Tue, 20 Jun 2023 17:11:29 +0200
Subject: [PATCH] =?UTF-8?q?st7789:=20fix=20scrolling=20when=20rotated=20by?=
 =?UTF-8?q?=20180=C2=B0?=
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This fixes https://github.com/tinygo-org/drivers/issues/573.
It doesn't handle 90° or 270°, I guess it needs a fix for 270° but I
haven't tested that so didn't include it in the patch.
---
 st7789/st7789.go | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/st7789/st7789.go b/st7789/st7789.go
index 5494203..1e6f128 100644
--- a/st7789/st7789.go
+++ b/st7789/st7789.go
@@ -558,7 +558,13 @@ func (d *Device) SetScrollArea(topFixedArea, bottomFixedArea int16) {
 		// The screen doesn't use the full 320 pixel height.
 		// Enlarge the bottom fixed area to fill the 320 pixel height, so that
 		// bottomFixedArea starts from the visible bottom of the screen.
-		bottomFixedArea += 320 - d.height
+		topFixedArea += d.rowOffset
+		bottomFixedArea += (320 - d.height) - d.rowOffset
+	}
+	if d.rotation == drivers.Rotation180 {
+		// The screen is rotated by 180°, so we have to switch the top and
+		// bottom fixed area.
+		topFixedArea, bottomFixedArea = bottomFixedArea, topFixedArea
 	}
 	verticalScrollArea := 320 - topFixedArea - bottomFixedArea
 	copy(d.buf[:6], []uint8{
@@ -572,6 +578,11 @@ func (d *Device) SetScrollArea(topFixedArea, bottomFixedArea int16) {
 
 // SetScroll sets the vertical scroll address of the display.
 func (d *Device) SetScroll(line int16) {
+	if d.rotation == drivers.Rotation180 {
+		// The screen is rotated by 180°, so we have to invert the scroll line
+		// (taking care of the RowOffset).
+		line = (319 - d.rowOffset) - line
+	}
 	d.buf[0] = uint8(line >> 8)
 	d.buf[1] = uint8(line)
 	d.startWrite()