[studio] Make clear screen before redraw

src/glutils/glutils.cpp

@@ -184,4 +184,9 @@ void sendEbo(const BufferSet &bs) noexcept {
 	glBufferData(GL_ELEMENT_ARRAY_BUFFER, bufferSize, bs.elements.data(), GL_STATIC_DRAW);
 }
 
+void clearScreen() noexcept {
+	glClearColor(0, 0, 0, 1);
+	glClear(GL_COLOR_BUFFER_BIT);
+}
+
 }