How to control device context in two ways

Code:

#include "sdl\SDL.h"

SDL_Texture* Image1;
SDL_Rect I1;
SDL_Surface* Image2;
SDL_Rect I2;

int testshow = 1;
int wmain()
{
	SDL_Window*    pWindow = NULL;
	SDL_Renderer*  pRenderer = NULL;
	SDL_Surface* screen = NULL;

	SDL_Init(SDL_INIT_EVERYTHING);
	pWindow = SDL_CreateWindow(u8"测试窗口", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 1920, 1080, SDL_WINDOW_SHOWN | SDL_WINDOW_ALLOW_HIGHDPI);

	pRenderer = SDL_CreateRenderer(pWindow, -1, 0);
	screen = SDL_GetWindowSurface(pWindow);

	//read 1.bmp 300x300 bgr
	char ImageBuffer[300 * 300 * 3];
	FILE* infile;
	_wfopen_s(&infile, L"1.bmp", L"rb");
	fseek(infile, 54, SEEK_SET);
	fread(ImageBuffer, sizeof(ImageBuffer), 1, infile);
	fclose(infile);
	SDL_Surface* buffer = SDL_CreateRGBSurfaceFrom(ImageBuffer, 300, 300, 3 * 8, 300 * 3, 0x0000FF, 0x00FF00, 0xFF0000, 0x000000);
	Image1 = SDL_CreateTextureFromSurface(pRenderer, buffer);
	I1.x = I1.y = 20;I1.w = I1.h = 300;

	//read 2.bmp 300x300 bgr
	_wfopen_s(&infile, L"2.bmp", L"rb");
	fseek(infile, 54, SEEK_SET);
	fread(ImageBuffer, sizeof(ImageBuffer), 1, infile);
	fclose(infile);
	Image2 = SDL_CreateRGBSurfaceFrom(ImageBuffer, 300, 300, 3 * 8, 300 * 3, 0x0000FF, 0x00FF00, 0xFF0000, 0x000000);
	I2.x = 350;I2.y = 20;I2.w = I2.h = 300;

	SDL_Event event;
	bool sQuit = false;
	while (!sQuit) 
	{
		while (SDL_PollEvent(&event))
		{
			switch (event.type)
			{
			case SDL_KEYDOWN:
				if (event.key.keysym.sym == SDLK_ESCAPE) 
				{
					sQuit = true;
				}
				if (event.key.keysym.sym == SDLK_1)
				{
					testshow = 1;
				}
				if (event.key.keysym.sym == SDLK_2) 
				{
					testshow = 2;
				}
				break;
			case SDL_QUIT:
				sQuit = true;
				break;
			default:
				break;
			}
		}
		
		//SDL_RenderClear(pRenderer);
		SDL_RenderCopy(pRenderer, Image1, NULL, &I1);//video card memory data
		SDL_BlitSurface(Image2, NULL, screen, &I2);//random access memory data

		//I want two methods for image render, but output image will flickering. could have only one.
		SDL_RenderPresent(pRenderer);//video card render mode
		SDL_UpdateWindowSurface(pWindow);//random access memory render mode

		/*
		switch (testshow)
		{
		case 1:
			SDL_RenderClear(pRenderer);
			SDL_RenderCopy(pRenderer, Image1, NULL, &I1);
			SDL_RenderPresent(pRenderer);
			break;
		case 2:
			SDL_BlitSurface(Image2, NULL, screen, &I2);
			SDL_UpdateWindowSurface(pWindow);
			break;
		}
		*/
	}
	SDL_Quit();
}




I want "SDL_RenderPresent" and "SDL_UpdateWindowSurface" in the same screen.
For example, “SDL_Texture” is normal image, “SDL_Surface” is Chinese characters. about render font, render “SDL_Surface”,Instead of from “SDL_Surface” to “SDL_Texture”.

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