Avoid some VC++ compiler warnings

src/modules/graphics/opengl/Canvas.cpp

@@ -396,7 +396,7 @@ void Canvas::setupGrab()
 	gl.setViewport({0, 0, width, height});
 
 	// Set up the projection matrix
-	gl.matrices.projection.push_back(Matrix::ortho(0.0, width, 0.0, height));
+	gl.matrices.projection.push_back(Matrix::ortho(0.0, (float) width, 0.0, (float) height));
 
 	// Make sure the correct sRGB setting is used when drawing to the canvas.
 	if (GLAD_VERSION_1_0 || GLAD_EXT_sRGB_write_control)

src/modules/graphics/opengl/Graphics.cpp

@@ -226,7 +226,7 @@ void Graphics::setViewportSize(int width, int height)
 	Canvas::systemViewport = gl.getViewport();
 
 	// Set up the projection matrix
-	gl.matrices.projection.back() = Matrix::ortho(0.0, width, height, 0.0);
+	gl.matrices.projection.back() = Matrix::ortho(0.0, (float) width, (float) height, 0.0);
 
 	// Restore the previously active Canvas.
 	setCanvas(canvases);

src/modules/graphics/opengl/Image.cpp

@@ -586,7 +586,7 @@ GLenum Image::getCompressedFormat(image::CompressedImageData::Format cformat) co
 
 bool Image::hasAnisotropicFilteringSupport()
 {
-	return GLAD_EXT_texture_filter_anisotropic;
+	return GLAD_EXT_texture_filter_anisotropic != GL_FALSE;
 }
 
 bool Image::hasCompressedTextureSupport(image::CompressedImageData::Format format, bool sRGB)

src/modules/graphics/opengl/Polyline.cpp

@@ -49,7 +49,7 @@ void Polyline::render(const float *coords, size_t count, size_t size_hint, float
 
 	// prepare vertex arrays
 	if (draw_overdraw)
-		halfwidth -= pixel_size * .3;
+		halfwidth -= pixel_size * 0.3f;
 
 	// compute sleeve
 	bool is_looping = (coords[0] == coords[count - 2]) && (coords[1] == coords[count - 1]);

src/modules/graphics/opengl/wrap_Graphics.cpp

@@ -494,8 +494,8 @@ int w_newShader(lua_State *L)
 		}
 	}
 
-	bool has_arg1 = lua_isstring(L, 1);
-	bool has_arg2 = lua_isstring(L, 2);
+	bool has_arg1 = lua_isstring(L, 1) != 0;
+	bool has_arg2 = lua_isstring(L, 2) != 0;
 
 	// require at least one string argument
 	if (!(has_arg1 || has_arg2))