ImageTree::getImageStream may sub a req for a .png with svg data

so we can't rely on the input path name as to its data format.
its going to be either png or data, so select which based on the first
byte, so presumably keeping the startup optimization of

commit 9e5cbcf90f15f46f84900a58bcaee437b98587f6
Date:   Wed Dec 18 15:35:19 2019 +0200
load images by explicit type

Change-Id: I0b2b743c138075f651d376767984be88745327a5
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/104287
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>

1 files changed, 11 insertions, 9 deletions

diff --git a/vcl/unx/gtk3/gtk3gtkinst.cxx b/vcl/unx/gtk3/gtk3gtkinst.cxx
index edd2d6bf63c5..acd917d27cf6 100644
--- a/vcl/unx/gtk3/gtk3gtkinst.cxx
+++ b/vcl/unx/gtk3/gtk3gtkinst.cxx
@@ -3224,13 +3224,16 @@ namespace
 
 namespace
 {
-    GdkPixbuf* load_icon_from_stream(SvMemoryStream& rStream, const OString& image_type)
+    GdkPixbuf* load_icon_from_stream(SvMemoryStream& rStream)
     {
-        // if we know the image type, it's a little faster to hand the type over and skip the type
-        // detection.
-        GdkPixbufLoader *pixbuf_loader = gdk_pixbuf_loader_new_with_type(image_type.getStr(), nullptr);
-        gdk_pixbuf_loader_write(pixbuf_loader, static_cast<const guchar*>(rStream.GetData()),
-                                rStream.TellEnd(), nullptr);
+        auto nLength = rStream.TellEnd();
+        if (!nLength)
+            return nullptr;
+        const guchar* pData = static_cast<const guchar*>(rStream.GetData());
+        assert((*pData == 137 || *pData == '<') && "if we want to support more than png or svg this function must change");
+        // if we know the image type, it's a little faster to hand the type over and skip the type detection.
+        GdkPixbufLoader *pixbuf_loader = gdk_pixbuf_loader_new_with_type(*pData == 137 ? "png" : "svg", nullptr);
+        gdk_pixbuf_loader_write(pixbuf_loader, pData, nLength, nullptr);
         gdk_pixbuf_loader_close(pixbuf_loader, nullptr);
         GdkPixbuf* pixbuf = gdk_pixbuf_loader_get_pixbuf(pixbuf_loader);
         if (pixbuf)
@@ -3244,8 +3247,7 @@ namespace
         auto xMemStm = ImageTree::get().getImageStream(rIconName, rIconTheme, rUILang);
         if (!xMemStm)
             return nullptr;
-        OUString sImageType = rIconName.copy(rIconName.lastIndexOf('.')+1).toAsciiLowerCase();
-        return load_icon_from_stream(*xMemStm, sImageType.toUtf8());
+        return load_icon_from_stream(*xMemStm);
     }
 }
 
@@ -3276,7 +3278,7 @@ namespace
         vcl::PNGWriter aWriter(aImage.GetBitmapEx(), &aFilterData);
         aWriter.Write(*xMemStm);
 
-        return load_icon_from_stream(*xMemStm, "png");
+        return load_icon_from_stream(*xMemStm);
     }
 
     GdkPixbuf* getPixbuf(const VirtualDevice& rDevice)