From ae3ea8875b9475532e5779154e3992affe2b9a32 Mon Sep 17 00:00:00 2001

From: Jan Blackquill <uhhadd@gmail.com>

Date: Tue, 24 Aug 2021 14:36:34 -0400

Subject: [PATCH 17/40] Correctly detect if image format is supported by

 QImageWriter

The code queries potential image formats by stripping a mimetype of its

'image/' prefix and making the rest of the mimetype capitalised, such as

'image/png' -> 'PNG'. The problem is that this is then searched for in

QImageWriter::supportedImageFormats() by simple equality. The method

returns a list of lowercase byte arrays, not uppercase. As the codepath

can never match due to checking for an uppercase word in an array of

lowercase words, this means that images are effectively always sent as

BMP format, even if they should be sent in other formats, such as PNG

or JPEG.

A simple inspection with GDB (or a qDebug) reveals this:

```

(gdb) p QImageWriter::supportedImageFormats()

$31 = {"bmp" = {...}, "bw" = {...}, "cur" = {...}, "eps" = {...},

  "epsf" = {...}, "epsi" = {...}, "icns" = {...},

  "ico" = {...}, "jp2" = {...}, "jpeg" = {...}, "jpg" = {...},

  "pbm" = {...}, "pcx" = {...}, "pgm" = {...},

  "pic" = {...}, "png" = {...}, "ppm" = {...},

  "rgb" = {...}, "rgba" = {...}, "sgi" = {...},

  "tga" = {...}, "tif" = {...}, "tiff" = {...},

  "wbmp" = {...}, "webp" = {...}, "xbm" = {...}, "xpm" = {...}}

```

```

(gdb) p QImageWriter::supportedImageFormats().contains("PNG")

$32 = false

```

```

(gdb) p QImageWriter::supportedImageFormats().contains("png")

$33 = true

```

The fix for this is simple: lowercase the remainder of the mimetype,

instead of uppercasing it, and we can start hitting the codepath that's

supposed to write non-BMP formats.

Change-Id: Id3e9b730b7edcabcb2f1b04d8ef0a4c1fb9c9159

Reviewed-by: David Edmundson <davidedmundson@kde.org>

Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

(cherry picked from commit 6072c1dc87e185f30c014f764737ac97b906640f)

---

 src/shared/qwaylandmimehelper.cpp | 2 +-

 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/shared/qwaylandmimehelper.cpp b/src/shared/qwaylandmimehelper.cpp

index a5fdd34d..051a91dc 100644

--- a/src/shared/qwaylandmimehelper.cpp

+++ b/src/shared/qwaylandmimehelper.cpp

@@ -60,7 +60,7 @@ QByteArray QWaylandMimeHelper::getByteArray(QMimeData *mimeData, const QString &

             buf.open(QIODevice::ReadWrite);

             QByteArray fmt = "BMP";

             if (mimeType.startsWith(QLatin1String("image/"))) {

-                QByteArray imgFmt = mimeType.mid(6).toUpper().toLatin1();

+                QByteArray imgFmt = mimeType.mid(6).toLower().toLatin1();

                 if (QImageWriter::supportedImageFormats().contains(imgFmt))

                     fmt = imgFmt;

             }

-- 

2.35.1