From 5de8f737237941df951c55bb504e2757d50bb475 Mon Sep 17 00:00:00 2001
From: Martin Kleusberg <mkleusberg@gmail.com>
Date: Thu, 5 Oct 2017 22:47:02 +0200
Subject: [PATCH] Use a more sophisticated method for detecting image data in
 Edit dialog

In the Edit Data dialog we check if the data contained in a cell is an
image. This check returned some false positives, so this commit adds
another more sophisticated check to work around that.

See issue #1138 and #1159.
---
 src/EditDialog.cpp | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/EditDialog.cpp b/src/EditDialog.cpp
index 610a293c..5daa4ebe 100644
--- a/src/EditDialog.cpp
+++ b/src/EditDialog.cpp
@@ -419,13 +419,12 @@ int EditDialog::checkDataType(const QByteArray& data)
         return Null;
     }
 
-    // Check if it's an image
+    // Check if it's an image. First do a quick test by calling canRead() which only checks the first couple of bytes or so. Only if
+    // that returned true, do a more sophisticated test of the data. This way we get both, good performance and proper data checking.
     QBuffer imageBuffer(&cellData);
     QImageReader readerBuffer(&imageBuffer);
-    bool someCheck = readerBuffer.canRead();
-    if (someCheck == true) {
+    if(readerBuffer.canRead() && !readerBuffer.read().isNull())
         return Image;
-    }
 
     // Check if it's text only
     if (QString(cellData).toUtf8() == cellData) { // Is there a better way to check this?