Fix bug #10718

Due to the peculiarities of Windows, it may happen that
pdftocairo is built without png support when compiled on this
platform. Unless explicitly requested (maybe for some peculiar
application and certainly not for usual distros), this is
highly improbable to occur on other platforms.

diff --git a/lib/scripts/legacy_lyxpreview2ppm.py b/lib/scripts/legacy_lyxpreview2ppm.py
index 99f4e56a7056ab80d82392572a5813bd7d28224f..c40cd8962c534ca8c1f6829b181c169d74657f64 100644 (file)
--- a/lib/scripts/legacy_lyxpreview2ppm.py
+++ b/lib/scripts/legacy_lyxpreview2ppm.py
@@ -417,6 +417,10 @@ def legacy_conversion_step3(latex_file, dpi, output_format, dvips_failed, skipMe
     pdftocairo = find_exe(["pdftocairo"])
     epstopdf   = find_exe(["epstopdf"])
     use_pdftocairo = pdftocairo != None and output_format == "png"
+    if use_pdftocairo and os.name == 'nt':
+        # On Windows, check for png support (see #10718)
+        conv_status, conv_stdout = run_command("%s --help" % pdftocairo)
+        use_pdftocairo = '-png' in conv_stdout
     if use_pdftocairo:
         conv = pdftocairo
     else: