Text: properly report failures from AbstractFontConverter.

doc/changelog.dox

@@ -174,6 +174,10 @@ See also:
 -   Properly zero-initializing the UTF-8 buffer in
     @ref Platform::GlfwApplication::textInputEvent() (see
     [mosra/magnum#324](https://github.com/mosra/magnum/pull/324))
+-   @ref Trade::AbstractFontConverter::exportFontToFile() and
+    @ref Trade::AbstractFontConverter::exportGlyphCacheToFile() now properly
+    returns failure when the underlying data export function returns an empty
+    list of files
 -   Updated the `base-qt` bootstrap project to correctly reset state tracker
     when going from and back to Qt code, and to use the framebuffer provided by
     Qt instead of @ref GL::defaultFramebuffer (see

src/Magnum/Text/AbstractFontConverter.cpp

@@ -121,6 +121,8 @@ bool AbstractFontConverter::doExportFontToFile(AbstractFont& font, AbstractGlyph
 
     /* Export all data */
     const auto data = doExportFontToData(font, cache, filename, characters);
+    if(data.empty()) return false;
+
     for(const auto& d: data) if(!Utility::Directory::write(d.first, d.second)) {
         Error() << "Text::AbstractFontConverter::exportFontToFile(): cannot write to file" << d.first;
         return false;
@@ -173,6 +175,8 @@ bool AbstractFontConverter::doExportGlyphCacheToFile(AbstractGlyphCache& cache,
 
     /* Export all data */
     const auto data = doExportGlyphCacheToData(cache, filename);
+    if(data.empty()) return false;
+
     for(const auto& d: data) if(!Utility::Directory::write(d.first, d.second)) {
         Error() << "Text::AbstractFontConverter::exportGlyphCacheToFile(): cannot write to file" << d.first;
         return false;

src/Magnum/Text/Test/AbstractFontConverterTest.cpp

@@ -44,9 +44,11 @@ struct AbstractFontConverterTest: TestSuite::Tester {
 
     void exportFontToSingleData();
     void exportFontToFile();
+    void exportFontToFileFailed();
 
     void exportGlyphCacheToSingleData();
     void exportGlyphCacheToFile();
+    void exportGlyphCacheToFileFailed();
 
     void importGlyphCacheFromSingleData();
     void importGlyphCacheFromFile();
@@ -57,9 +59,11 @@ AbstractFontConverterTest::AbstractFontConverterTest() {
 
               &AbstractFontConverterTest::exportFontToSingleData,
               &AbstractFontConverterTest::exportFontToFile,
+              &AbstractFontConverterTest::exportFontToFileFailed,
 
               &AbstractFontConverterTest::exportGlyphCacheToSingleData,
               &AbstractFontConverterTest::exportGlyphCacheToFile,
+              &AbstractFontConverterTest::exportGlyphCacheToFileFailed,
 
               &AbstractFontConverterTest::importGlyphCacheFromSingleData,
               &AbstractFontConverterTest::importGlyphCacheFromFile});
@@ -160,6 +164,16 @@ void AbstractFontConverterTest::exportFontToFile() {
                        "\xfe\xed", TestSuite::Compare::FileToString);
 }
 
+void AbstractFontConverterTest::exportFontToFileFailed() {
+    struct: AbstractFontConverter {
+        Features doFeatures() const override { return Feature::ConvertData|Feature::ExportFont|Feature::MultiFile; }
+
+        std::vector<std::pair<std::string, Containers::Array<char>>> doExportFontToData(AbstractFont&, AbstractGlyphCache&, const std::string&, const std::u32string&) const override { return {}; }
+    } exporter;
+
+    CORRADE_VERIFY(!exporter.exportFontToFile(dummyFont, dummyGlyphCache, "nonexistent.dat", {}));
+}
+
 void AbstractFontConverterTest::exportGlyphCacheToSingleData() {
     struct: Text::AbstractFontConverter {
         Features doFeatures() const override { return Feature::ConvertData|Feature::ExportGlyphCache; }
@@ -207,6 +221,17 @@ void AbstractFontConverterTest::exportGlyphCacheToFile() {
                        "\xfe\xed", TestSuite::Compare::FileToString);
 }
 
+void AbstractFontConverterTest::exportGlyphCacheToFileFailed() {
+    struct: Text::AbstractFontConverter {
+        Features doFeatures() const override { return Feature::ConvertData|Feature::ExportGlyphCache|Feature::MultiFile; }
+
+        std::vector<std::pair<std::string, Containers::Array<char>>> doExportGlyphCacheToData(AbstractGlyphCache&, const std::string&) const override { return {}; }
+    } exporter;
+
+    /* doExportGlyphCacheToFile() should call doExportGlyphCacheToData() */
+    CORRADE_VERIFY(!exporter.exportGlyphCacheToFile(dummyGlyphCache, "nonexistent.dat"));
+}
+
 class SingleGlyphCacheDataImporter: public Text::AbstractFontConverter {
     private:
         Features doFeatures() const override { return Feature::ConvertData|Feature::ImportGlyphCache; }