Error message when trying to save a screenshot in an unsupported format

(cherry-picked from commit 93f956ed4c)

src/editor/controller/editor_controller.cpp

@@ -190,7 +190,7 @@ void editor_controller::do_screenshot(const std::string& screenshot_filename /*
 {
 	try {
 		surface screenshot = gui().screenshot(true);
-		if(screenshot.null() || !image::save_image(screenshot, screenshot_filename)) {
+		if(screenshot.null() || image::save_image(screenshot, screenshot_filename) != image::save_result::success) {
 			ERR_ED << "Screenshot creation failed!\n";
 		}
 	} catch (wml_exception& e) {

src/game_launcher.cpp

@@ -601,7 +601,7 @@ bool game_launcher::play_render_image_mode()
 		outfile = *cmdline_opts_.render_image_dst;
 	}
 
-	if (!image::save_image(*cmdline_opts_.render_image, outfile)) {
+	if (image::save_image(*cmdline_opts_.render_image, outfile) != image::save_result::success) {
 		exit(1);
 	}
 

src/gui/dialogs/screenshot_notification.cpp

@@ -35,6 +35,7 @@
 #include "gettext.hpp"
 
 #include <boost/filesystem.hpp>
+#include <stdexcept>
 
 namespace gui2
 {
@@ -124,11 +125,16 @@ void screenshot_notification::save_screenshot()
 	boost::filesystem::path path(screenshots_dir_path_);
 	path /= filename;
 
-	const bool res = image::save_image(screenshot_, path.string());
-	if(!res) {
+	image::save_result res = image::save_image(screenshot_, path.string());
+	if(res == image::save_result::unsupported_format) {
+		gui2::show_error_message(_("Unsupported image format.\n\n"
+			"Try to save the screenshot as PNG instead."));
+	} else if(res == image::save_result::save_failed) {
 		gui2::show_error_message(
 			translation::dsgettext("wesnoth", "Screenshot creation failed.\n\n"
-				"Make sure there is enough space on the drive holding Wesnoth’s player resource files and that file permissions are set up correctly."));
+			"Make sure there is enough space on the drive holding Wesnoth’s player resource files and that file permissions are set up correctly."));
+	} else if(res != image::save_result::success) {
+		throw std::logic_error("Unexpected error while trying to save a screenshot");
 	} else {
 		path_box.set_active(false);
 		find_widget<button>(&window, "open", false).set_active(true);

src/image.cpp

@@ -1285,15 +1285,15 @@ bool precached_file_exists(const std::string& file)
 	return false;
 }
 
-bool save_image(const locator& i_locator, const std::string& filename)
+save_result save_image(const locator& i_locator, const std::string& filename)
 {
 	return save_image(get_image(i_locator), filename);
 }
 
-bool save_image(const surface& surf, const std::string& filename)
+save_result save_image(const surface& surf, const std::string& filename)
 {
 	if(surf.null()) {
-		return false;
+		return save_result::no_image;
 	}
 
 #ifdef SDL_IMAGE_VERSION_ATLEAST
@@ -1302,7 +1302,7 @@ bool save_image(const surface& surf, const std::string& filename)
 		LOG_DP << "Writing a JPG image to " << filename << std::endl;
 
 		const int err = IMG_SaveJPG_RW(surf, filesystem::make_write_RWops(filename).release(), true, 75); // SDL takes ownership of the RWops
-		return err == 0;
+		return err == 0 ? save_result::success : save_result::save_failed;
 	}
 #endif
 #endif
@@ -1311,11 +1311,16 @@ bool save_image(const surface& surf, const std::string& filename)
 		LOG_DP << "Writing a PNG image to " << filename << std::endl;
 
 		const int err = IMG_SavePNG_RW(surf, filesystem::make_write_RWops(filename).release(), true); // SDL takes ownership of the RWops
-		return err == 0;
+		return err == 0 ? save_result::success : save_result::save_failed;
 	}
 
-	LOG_DP << "Writing a BMP image to " << filename << std::endl;
-	return SDL_SaveBMP(surf, filename.c_str()) == 0;
+	if(filesystem::ends_with(filename, ".bmp")) {
+		LOG_DP << "Writing a BMP image to " << filename << std::endl;
+		const int err = SDL_SaveBMP(surf, filename.c_str()) == 0;
+		return err == 0 ? save_result::success : save_result::save_failed;
+	}
+
+	return save_result::unsupported_format;
 }
 
 bool update_from_preferences()

src/image.hpp

@@ -222,6 +222,8 @@ namespace image {
 	/// initialize any private data, e.g. algorithm choices from preferences
 	bool update_from_preferences();
 
-	bool save_image(const locator& i_locator, const std::string& outfile);
-	bool save_image(const surface& surf, const std::string& outfile);
+	enum class save_result {success, unsupported_format, save_failed, no_image};
+
+	save_result save_image(const locator& i_locator, const std::string& outfile);
+	save_result save_image(const surface& surf, const std::string& outfile);
 }