When creating a new graphics sheet, initialize it with a convenient checkerboard pattern

- Also fix a crash when first creating a graphics sheet in a scenario due to the temporary folder not being in the image search paths

src/scenedit/scen.core.cpp

@@ -3378,9 +3378,10 @@ void edit_custom_sheets() {
 		spec_scen_g.clear();
 		spec_scen_g.sheets = new sf::Texture[1];
 		spec_scen_g.numSheets = 1;
-		spec_scen_g.sheets[0].create(280, 360);
+		spec_scen_g.init_sheet(0);
 		spec_scen_g.sheets[0].copyToImage().saveToFile((pic_dir/"sheet0.png").string().c_str());
 		all_pics.insert(all_pics.begin(), 0);
+		ResMgr::pushPath<ImageRsrc>(pic_dir);
 	}
 	
 	set_cursor(watch_curs);
@@ -3468,7 +3469,7 @@ void edit_custom_sheets() {
 			sf::Texture* wasSheets = spec_scen_g.sheets;
 			spec_scen_g.sheets = new sf::Texture[spec_scen_g.numSheets + 1];
 			std::copy_n(wasSheets, spec_scen_g.numSheets, spec_scen_g.sheets);
-			spec_scen_g.sheets[newSheet].create(280,360);
+			spec_scen_g.init_sheet(newSheet);
 			spec_scen_g.sheets[newSheet].copyToImage().saveToFile(sheetPath.string().c_str());
 			spec_scen_g.numSheets++;
 			auto iter = all_pics.insert(std::upper_bound(all_pics.begin(), all_pics.end(), newSheet), newSheet);

src/tools/graphtool.cpp

@@ -535,6 +535,22 @@ void cCustomGraphics::replace_sheet(size_t num, sf::Image& newSheet) {
 	ResMgr::free<ImageRsrc>(sheetname);
 }
 
+void cCustomGraphics::init_sheet(size_t num) {
+	sheets[num].create(280,360);
+	sf::Image fill1, fill2;
+	fill1.create(28,36,{0xff,0xff,0xc0});
+	fill2.create(28,36,{0xc0,0xff,0xc0});
+	for(int y = 0; y < 10; y++) {
+		for(int x = 0; x < 10; x++) {
+			if(x % 2 == y % 2) {
+				sheets[num].update(fill1.getPixelsPtr(), 28, 36, x * 28, y * 36);
+			} else {
+				sheets[num].update(fill2.getPixelsPtr(), 28, 36, x * 28, y * 36);
+			}
+		}
+	}
+}
+
 // TODO: This doesn't belong in this file
 std::string get_str(std::string list, short j){
 	if(j == 0) return list;

src/tools/graphtool.hpp

@@ -83,6 +83,7 @@ struct cCustomGraphics {
 	graf_pos find_graphic(pic_num_t pic, bool party = false);
 	size_t count(bool party = false);
 	void replace_sheet(size_t num, sf::Image& newSheet);
+	void init_sheet(size_t num);
 };
 
 struct snippet_t {