i'm fairly new at programming with allegro, and i wanna change the background color of my programs from something more pleasant than black haha :) can some one help please?
and just for a reference of what im doing
#include <allegro.h>
BITMAP* buffer;
BITMAP* bmp;
int cursor_x = 20;
int cursor_y = 20;
int getMouseInfo(){
if(mouse_b & 1){
cursor_x = mouse_x;
cursor_y = mouse_y;
return 1;
}
return 0;
}
void updateScreen(){
show_mouse(NULL);
circlefill ( buffer, cursor_x, cursor_y, 60, makecol( 0, 255 , 0));
draw_sprite( screen, buffer, 0, 0);
}
int main(){
allegro_init();
install_mouse();
install_keyboard();
set_color_depth(16);
set_gfx_mode( GFX_AUTODETECT, 640, 480, 0, 0);
rectfill (
buffer = create_bitmap( 640, 480);
show_mouse(screen);
while( !key[KEY_ESC])
{
int switcher=1;
while(getMouseInfo())
{
updateScreen();
if(getMouseInfo()==0) switcher=0;
}
if(switcher==0) show_mouse(screen);
}
return 0;
}
END_OF_MAIN();
To create backgroud bitmap try this:
/* Make a bitmap in RAM. */
BITMAP *bmp = create_bitmap(SCR_X, SCR_Y);
then try this to clear bmp to some different color:
/* Clear the screen to red. */
clear_to_color(bmp, makecol(255, 0, 0));
or this to load bitmap from file:
bmp = load_bitmap("image.pcx", palette);
Then you just need to blit this bitmap with your screen - like this:
/* Blit bmp on the screen. */
blit(bmp, screen, 0, 0, 0, 0, bmp->w, bmp->h);
Draw a screen-sized rectangle that is the color you want the background to be. Or just use clear_bitmap to clear the screen.
#include <iostream>
using namespace std;
int main()
{
cout<<" In the world were gamers play MINECRAFT, where they creating everithing they can emagine ...\n";
cin.get();
return 0;
}
Related
I am trying to create a transparent surface, blit it bigger surface (size of my screen), then create a texture of it, copy to the renderer, and finaly render present.
I have seen many other forums saying I have to use SetBlendMode (for surface, texture, and renderer), ColorKey, SetSurfaceBlendMode. I tried them all but I can't seem to get it to work. I read that SDL_BlitScaled is not suitable for combining surfaces that have transparent pixels, but I am completely lost as to what I have to do instead.
What I noticed, when I use SDL_CreateRGBSurface (with an alpha value) to create a surface, the surface's PixelFormat is RGB888 instead of RGBA8888 (what I am expecting since I provide the alpha value). Using SDL_ConvertSurfaceFormat did not help.
Can somebody tell me what I am missing?
Complete code: removed, my appologies
Please note that I have removed the attempts to get transparency working
The renderer:
mRenderer = SDL_CreateRenderer(mWindow, -1, SDL_RENDERER_ACCELERATED);
My render loop:
void CApp::Render()
{
SDL_RenderClear(mRenderer);
mBackGround->Render(mRenderer);
mForeGround->Render(mRenderer);
SDL_RenderPresent(mRenderer);
}
The big surface I am blitting to:
mSurface = SDL_CreateRGBSurface(0, CApp::Window_W(), CApp::Window_H(), 32, 0, 0, 0, 0);
The code to get tiles from a spritesheet:
bool Map::GetTilesFromSpriteSheet(SDL_Surface *pSpriteSheet, int pTile_w, int pTile_h)
{
if(pSpriteSheet->w % pTile_w == 0 && pSpriteSheet->h % pTile_h == 0) {
SDL_Rect srcRect;
srcRect.w = pTile_w;
srcRect.h = pTile_h;
for(int y = 0; y < pSpriteSheet->h / pTile_h; y++) {
for(int x = 0; x < pSpriteSheet->w / pTile_w; x++) {
srcRect.x = x*pTile_w;
srcRect.y = y*pTile_h;
SDL_Surface* tempSurface = SDL_CreateRGBSurface(0, pTile_w, pTile_h, 32, 0, 0, 0, 0);
if(SDL_BlitSurface(pSpriteSheet, &srcRect, tempSurface, nullptr)==0) {
mTiles.push_back(tempSurface);
} else {
Log("Error extracting tile (%d,%d)(w,h): %s", x, y, SDL_GetError());
return false;
}
}
}
Log("Number of tiles: %d", static_cast<int>(mTiles.size()));
} else {
Log("Background spritesheet is incompatible with tile dimensions (%d,%d)(w,h).", pTile_w, pTile_h);
return false;
}
return true;
}
This is where I combine the tiles to create the big surface:
bool Map::GenerateMap(std::vector<std::vector<int>> &pMap, std::vector<SDL_Surface*> &pTiles, SDL_Surface* pDestination)
{
SDL_Rect rect;
rect.w = mDstTile_W;
rect.h = mDstTile_H;
SDL_Surface* transparent = SDL_CreateRGBSurface(0, mDstTile_W, mDstTile_H, 32, 0, 0, 0, 0);
for(int y = 0; y < static_cast<int>(pMap.size()); y++) {
for(int x = 0; x < static_cast<int>(pMap.at(static_cast<unsigned long>(y)).size()); x++) {
rect.x = x*mDstTile_W;
rect.y = y*mDstTile_H;
int index = static_cast<int>(pMap.at(static_cast<unsigned long>(y)).at(static_cast<unsigned long>(x)));
if(index < 0) {
if(SDL_BlitScaled(transparent, nullptr, pDestination, &rect) != 0) {
Log("Error blitting transparent surface to destination: %s", SDL_GetError());
}
} else if(SDL_BlitScaled(pTiles[static_cast<unsigned long>(index)],
nullptr, pDestination, &rect) != 0) {
Log("Error blitting surface to destination: %s", SDL_GetError());
return false;
}
}
}
SDL_FreeSurface(transparent);
return true;
}
And finaly, this is the code to render the big surface to the screen, first by creating a texture:
void ForeGround::Render(SDL_Renderer* pRenderer)
{
if(mTexture) SDL_DestroyTexture(mTexture);
mTexture = SDL_CreateTextureFromSurface(pRenderer, mSurface);
if(mTexture == nullptr) {
Log("Unable to create foreground texture: %s", SDL_GetError());
} else if (SDL_RenderCopy(pRenderer, mTexture, nullptr, nullptr)) {
Log("Unable to render foreground: %s", SDL_GetError());
}
}
As #keltar mentioned, I was not creating surfaces with an alpha value.
I had to change the SDL_CreateRGBSurface call. The code snippet below creates an empty, transparent surface where I can blit to if needed (for example, tiles from a spritesheet).
SDL_Surface* tempSurface = SDL_CreateRGBSurface(..., 32, 0xff, 0xff00, 0xff0000, 0xff000000);
The code snippet below creates a black, non-transparent surface.
SDL_Surface* tempSurface = SDL_CreateRGBSurface(..., 32, 0xff, 0xff00, 0xff0000, 0x00000000);
This was enough for me, I did not have to use SDL_SetRenderDrawBlendMode, SDL_SetSurfaceBlendMode, SDL_SetTextureBlendMode, or SDL_ConvertSurface. A quick look at the SDL wiki showed:
By default surfaces with an alpha mask are set up for blending as with
SDL_SetSurfaceBlendMode(surface, SDL_BLENDMODE_BLEND)
Which explained why I did not have to call any of those functions. A big shout-out to keltar for his quick answer!
The problem with my code is that I am making a pong game in SDL 2.0 in c++. I did everything until creating the movement. When the player paddle moves, it leaves behind a trail in the same color as the paddle. I watched some videos on YouTube, but when they do the movement it's nice and clear and for me to fix this but I need to recolor the background every time the player moves, which makes it being all flashy and if I hold the button I don't see the paddle at all.
#include<iostream>
#include<SDL2/SDL.h>
#include<SDL2/SDL_image.h>
#include<windows.h>
#define width 800
#define height 600
using namespace std;
bool run = true;
class Player{
private:
SDL_Window* window = SDL_CreateWindow("Pong!", SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED, width, height, SDL_WINDOW_RESIZABLE);
SDL_Surface* Screen = SDL_GetWindowSurface(window);
Uint32 screen_color = SDL_MapRGB(Screen->format, 0, 0, 0);
Uint32 In_game_RGB = SDL_MapRGB(Screen->format, 255, 255, 255);
SDL_Rect Pl;
SDL_Rect AI;
SDL_Rect Ball;
SDL_Rect ClearP;
SDL_Rect ClearAI;
public:
Player(){
//Player parameters
Pl.x = 60;Pl.y = 225;Pl.w = 25;Pl.h = 200;
//AI parameters
AI.x = 720;AI.y = 225;AI.w = 25;AI.h = 200;
//Ball parameters
Ball.x = width/2;Ball.y = height/2+10;Ball.w = 25;Ball.h = 25;
//Recoloring parameters
ClearP.x = 0;ClearP.y = 0; ClearP.w = 375;ClearP.h = height;
ClearAI.x = 425;ClearAI.y = 0;ClearAI.w = 375;ClearAI.h = height;
//Make the screen color black
SDL_FillRect(Screen, NULL, screen_color);
}
void scrUpdate(){
SDL_UpdateWindowSurface(window);
}
void drawPlayer(){
SDL_FillRect(Screen, &Pl, In_game_RGB);
}
void drawComputer(){
SDL_FillRect(Screen, &AI, In_game_RGB);
}
void ball(){
SDL_FillRect(Screen, &Ball, In_game_RGB);
}
void Movement(){
if(GetAsyncKeyState(VK_DOWN)){
Pl.y += 2;
SDL_FillRect(Screen,&ClearP,screen_color);
}
if(GetAsyncKeyState(VK_UP)){
SDL_FillRect(Screen,&ClearP,screen_color);
Pl.y -= 2;
}
}
};
void EventCheck(){
SDL_Event event;
if(SDL_PollEvent(&event)){
if(event.type == SDL_QUIT){
run = false;
}
}
}
int main( int argc, char *argv[] )
{
SDL_Init(SDL_INIT_EVERYTHING);
Player Play;
//Player Computer();
while(run){
Play.scrUpdate();
Play.drawPlayer();
Play.drawComputer();
Play.ball();
Play.Movement();
EventCheck();
}
SDL_Quit();
return EXIT_SUCCESS;
}
It would help to show some code or an example of what you have been doing, or a link to one of the videos you have been watching:
Youtube tutorial
but I suggest taking a look at:
screen = SDL_SetVideoMode(800, 600, 32, SDL_HWSURFACE); and SDL_Flip(screen) as those have to do with screen buffering and drawing.
Another possibilty is that you are running an outdated version of SDL, or an incompatible one with your current system.
To be able to give a more complete and proper answer, I'd highly suggest adding more information about your code, screenshots of results and your version of SDL and operating system.
Also, you said it was flashy when you hold the paddle. I think it must be that you are performing your logic to move the paddle and you redraw the paddle once it's still. If you are redrawing the entire screen constantly, consider double buffering.
im trying to show two different animations made with two functions, one render and two threads.
Im getting different kind of error each time i run the code.
Such as: segmentation default in the refresh function (line SDL_RenderPresent(w1.renderer);) and other strange errors too. Everytime is different.
I know its about using the render in both different threads. But i dont know how to solve this problem.
When i run with just one of the threads everything its ok. But not with the two of them.
I just want to show different graphics playing around the window. (always using sdl2).
Here is my code:
window.h:
class Window
{
public:
SDL_Window *window1;
int background,windowWidth,windowHeight,windowXcoord,windowYcoord;
SDL_Renderer * renderer;
SDL_Renderer * renderer2;
Window();
};
void refresh();
extern Window w1;
window.cpp:
Window w1;
Window::Window()
{
window1=nullptr;
background = 0xffffff;
windowWidth=700; windowHeight=500;
windowXcoord = 650; windowYcoord = 0;
this->window1 =
SDL_CreateWindow("Window",windowXcoord,windowYcoord,
windowWidth,windowHeight, SDL_WINDOW_SHOWN);
this->renderer = SDL_CreateRenderer( this->window1, -1 ,
SDL_RENDERER_ACCELERATED);
SDL_SetRenderDrawColor( this->renderer, 255, 255, 255, 255 );
SDL_RenderClear( this->renderer );
SDL_RenderPresent(this->renderer);
}
// this function is called everytime an object or function want to "refresh" the window.
void refresh(){
// clearing the window
SDL_SetRenderDrawColor( w1.renderer, 255, 255, 255,0 );
SDL_RenderClear( w1.renderer );
// r1, the first Rects object to animate.
SDL_SetRenderDrawColor( w1.renderer,255,0,0,255);
SDL_RenderFillRect( w1.renderer, &r1.rect );
// r2, the second Rects.
SDL_SetRenderDrawColor( w1.renderer,255,0,255,255);
SDL_RenderFillRect( w1.renderer, &r2.rect );
SDL_RenderPresent(w1.renderer);
}
rects.h:
class Rects
{
public:
SDL_Rect rect;
Rects();
};
extern Rects r1, r2;
void moveR1();
void moveR2();
rects.cpp:
Rects::Rects()
{ }
Rects r1,r2;
// moveR1 and moveR2, (just some dumm animations-example)
void moveR1(){
r1.rect.x=400; r1.rect.y=100;
r1.rect.w =40; r1.rect.h =10;
SDL_SetRenderDrawColor( w1.renderer,255,0,0,255);
SDL_RenderFillRect( w1.renderer, &r1.rect );
{
for (int u = 1; u<=5;u++){
r1.rect.x=200; r1.rect.y=100;
r1.rect.w =50; r1.rect.h =50;
refresh();
for (int i = 1; i <=200; i++){
r1.rect.x-=1;
usleep (7000);
refresh();
}
}
}
}
void moveR2(){
r2.rect.x=200; r2.rect.y=100;
r2.rect.w =40; r2.rect.h =10;
SDL_SetRenderDrawColor( w1.renderer,255,255,0,255);
SDL_RenderFillRect( w1.renderer, &r2.rect );
{
for (int u = 1; u<=5;u++){
check
r2.rect.x=200; r2.rect.y=100;
r2.rect.w =50; r2.rect.h =50;
refresh();
for (int i = 1; i <=200; i++){
r2.rect.x+=1; r2.rect.y+=1;
usleep (7000);
refresh();
}
}
}
}
and the main:
int main()
{
thread t1(moveR1);
t1.detach();
thread t2(moveR2);
t2.detach();
// sleep instead of showing a loop.
sleep (10);
return 0;
}
any polite help is welcome, im here to learn.
When i run with just one of the threads everything its ok. But not with the two of them.
According to the documentation for 2D accelerated rendering (also known as SDL_render.h, in other terms the place where SDL_RenderPresent lives):
This API is not designed to be used from multiple threads, see SDL bug #1995 for details.
You won't be able to do that any time soon. By looking at the description of the error, it looks like an UB and the link to the bug gives you all the details probably.
I just want to show different graphics playing around the window.
You don't need to use two threads to do that.
You can just update positions, animations and whatever is needed for your graphics and show them from the same thread. Nothing prevents you from calling the same function (as an example SDL_RenderCopy) more than once before to invoke SDL_RenderPresent.
If you needed a thread per graphic, what about a game with thousands of polygons on video?
// thanks to skypjack, i am able to solve the problem
// HOW TO PRESENT TWO (OR MORE) GRAPHICS WITH SDL_RENDERER WITHOUT USING THREADS.
// The two rectangle animation are just and example.
// It could be whatever we want to show.
// In this case, just two rectangles moving around.
#include <unistd.h>
#include <SDL.h>
using namespace std;
SDL_Window *window1;
int background, windowWidth, windowHeight,windowXcoord,
windowYcoord;
SDL_Rect rectangle1;
SDL_Rect rectangle2;
SDL_Renderer *renderer;
int sequence1;
int sequence2;
void moveRectangle1(), moveRectangle2();
int main()
{
window1=nullptr;
background = 0xffffff;
windowWidth=700; windowHeight=500;
windowXcoord = 650; windowYcoord = 0;
window1 = SDL_CreateWindow("Main
Window",windowXcoord,windowYcoord, windowWidth,windowHeight,
SDL_WINDOW_SHOWN);
renderer = SDL_CreateRenderer( window1, -1 ,
SDL_RENDERER_ACCELERATED);
SDL_SetRenderDrawColor( renderer, 255, 255, 255, 255 );
SDL_RenderClear( renderer );
SDL_RenderPresent(renderer);
rectangle1.x = 100; rectangle1.y = 100; rectangle1.h = 40;
rectangle1.w = 40;
rectangle2.x = 100; rectangle2.y = 100; rectangle2.h = 40;
rectangle2.w = 40;
for (int i = 1;i<500;i++){
SDL_SetRenderDrawColor( renderer, 255, 255, 255,0 );
SDL_RenderClear( renderer );
// chequear return (cerrar programa)
moveRectangle1();
moveRectangle2();
SDL_RenderPresent(renderer);
usleep (12000);
}
return 0;
}
void moveRectangle1(){
sequence1++;
if (sequence1 <= 50){ rectangle1.x++; }
else if (sequence1 <= 100){ rectangle1.x--; }
else { sequence1 = 0; }
SDL_SetRenderDrawColor(renderer,255,0,0,255);
SDL_RenderFillRect(renderer, &rectangle1 );
}
void moveRectangle2(){
sequence2++;
if (sequence2 <= 100){ rectangle2.y++; }
else if (sequence2 <= 200){ rectangle2.y--; }
else { sequence2 = 0; }
SDL_SetRenderDrawColor(renderer,0,200,0,255);
SDL_RenderFillRect( renderer, &rectangle2 );
}
So I've been practicing/making a quick game for the past 6 hours, then something stumped me.
The game had an integer, Score, which would be added up with one every time an ammo hits an alien.
int Score;
stringstream sstr;
sstr << Score;
string str1 = sstr.str();
TTF_Font* Sans = NULL;
Sans = TTF_OpenFont("Sans.ttf", 24);
SDL_Color White = {255, 255, 255};
SDL_Surface* surfaceMessage = NULL;
surfaceMessage = TTF_RenderText_Solid(Sans, str1.c_str(), White);
SDL_Texture* Message = NULL;
Message = SDL_CreateTextureFromSurface(renderer, surfaceMessage);
SDL_Rect Message_rect;
Message_rect.x = 0;
Message_rect.y = 0;
Message_rect.w = 100;
Message_rect.h = 100;
//UPDATE/GAMELOOP AREA, I DIDN'T REALLY PASTE THE WHOLE PART
SDL_RenderCopy(renderer, Message, NULL, &Message_rect);
Now I've been trying different roundabouts as to how to update the texture, Message.
I made a cout check to check if I did hit an alien and what my current score is, it appears perfectly fine, but the rendered texture, Message won't move from 0.
I created a texture from the surface (the message) because I mostly prefer textures and I don't have any surface since in my current knowledge, you'd at least need a filled surface where you could blitz this
And another question, I'm planning to make a dialogue heavy game, is there another way of doing the texts? I've got a strong feeling that I'm doing it wrong.
Minimal runnable example
The counter gets updated every second.
Ubuntu 16.10, SDL 2.0.4:
sudo apt-get install libsdl2-dev libsdl2-ttf-dev
./main /path/to/my.ttf
This method is easy to integrate, but not very efficient as it re-rasters and re-creates textures all the time. If you also want efficiency, see: Rendering fonts and text with SDL2 efficiently I get 4k FPS, so it might be fine for simple applications.
GitHub upstream with a ttf file to test with: https://github.com/cirosantilli/cpp-cheat/blob/d36527fe4977bb9ef4b885b1ec92bd0cd3444a98/sdl/ttf.c:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL_ttf.h>
#define COMMON_COLOR_MAX 255
#define COMMON_WINDOW_WIDTH 500
#define COMMON_WINDOW_HEIGHT (COMMON_WINDOW_WIDTH)
double common_get_secs(void) {
struct timespec ts;
timespec_get(&ts, TIME_UTC);
return ts.tv_sec + (1e-9 * ts.tv_nsec);
}
const double COMMON_FPS_GRANULARITY_S = 0.5;
double common_fps_last_time_s;
unsigned int common_fps_nframes;
void common_fps_init() {
common_fps_nframes = 0;
common_fps_last_time_s = common_get_secs();
}
void common_fps_update_and_print() {
double dt, current_time_s;
current_time_s = common_get_secs();
common_fps_nframes++;
dt = current_time_s - common_fps_last_time_s;
if (dt > COMMON_FPS_GRANULARITY_S) {
printf("FPS = %f\n", common_fps_nframes / dt);
common_fps_last_time_s = current_time_s;
common_fps_nframes = 0;
}
}
#define MAX_STRING_LEN 4
/*
- x, y: upper left corner of string
- rect output Width and height contain rendered dimensions.
*/
void render_text(
SDL_Renderer *renderer,
int x,
int y,
const char *text,
TTF_Font *font,
SDL_Rect *rect,
SDL_Color *color
) {
SDL_Surface *surface;
SDL_Texture *texture;
surface = TTF_RenderText_Solid(font, text, *color);
texture = SDL_CreateTextureFromSurface(renderer, surface);
rect->x = x;
rect->y = y;
rect->w = surface->w;
rect->h = surface->h;
/* This is wasteful for textures that stay the same.
* But makes things less stateful and easier to use.
* Not going to code an atlas solution here... are we? */
SDL_FreeSurface(surface);
SDL_RenderCopy(renderer, texture, NULL, rect);
SDL_DestroyTexture(texture);
}
int main(int argc, char **argv) {
SDL_Color color;
SDL_Event event;
SDL_Rect rect;
SDL_Renderer *renderer;
SDL_Window *window;
char *font_path, text[MAX_STRING_LEN];
/* CLI arguments. */
if (argc == 1) {
font_path = "FreeSans.ttf";
} else if (argc == 2) {
font_path = argv[1];
} else {
fprintf(stderr, "error: too many arguments\n");
exit(EXIT_FAILURE);
}
/* initialize variables. */
color.r = COMMON_COLOR_MAX;
color.g = COMMON_COLOR_MAX;
color.b = COMMON_COLOR_MAX;
color.a = COMMON_COLOR_MAX;
/* Init window. */
SDL_Init(SDL_INIT_TIMER | SDL_INIT_VIDEO);
SDL_CreateWindowAndRenderer(
COMMON_WINDOW_WIDTH,
COMMON_WINDOW_WIDTH,
0,
&window,
&renderer
);
/* Init TTF. */
TTF_Init();
TTF_Font *font = TTF_OpenFont(font_path, 24);
if (font == NULL) {
fprintf(stderr, "error: font not found\n");
exit(EXIT_FAILURE);
}
/* Main loop. */
common_fps_init();
while (1) {
if (SDL_PollEvent(&event) && event.type == SDL_QUIT) {
break;
}
/* Use TTF. */
SDL_SetRenderDrawColor(renderer, 0, 0, 0, 0);
SDL_RenderClear(renderer);
render_text(renderer, 0, 0, "hello", font, &rect, &color);
render_text(renderer, 0, rect.y + rect.h, "world", font, &rect, &color);
snprintf(text, MAX_STRING_LEN, "%u", (unsigned int)(time(NULL) % 1000));
render_text(renderer, 0, rect.y + rect.h, text, font, &rect, &color);
SDL_RenderPresent(renderer);
common_fps_update_and_print();
}
/* Cleanup. */
TTF_Quit();
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
SDL_Quit();
return EXIT_SUCCESS;
}
Well, obviously you need to recreate texture from surface with new text each time your score changes. That is not very efficient for texts that change frequently (since you create/destroy a lot of surfaces/textures), but can be fine for small games (since modern computers are very powerful).
But generally, as mentioned in comments, for this case font atlases are used with combination of custom text renderers. The trick is to store all characters in one texture and render its regions multiple times to produce necessary text. The AngelCode BMFont is popuar tool for creating font atlases.
For maximum performance both approaches are used in combination: precreated textures for static text, and font atlases for dynamic text.
(See "Edit 2" below for the solution.)
I need to create SDL surfaces from scratch, instead of loading them from a file. Unfortunately, SDL_BlitSurface() seems to render all colors as black when used with the surface generated through SDL_CreateRGBSurface(). This is my code:
int main(int argc, char** argv)
{
SDL_Surface* screen = SDL_SetVideoMode(640, 480, 32, SDL_HWSURFACE);
SDL_Surface* layer = SDL_CreateRGBSurface(SDL_HWSURFACE, 100, 100,
screen->format->BitsPerPixel,
screen->format->Rmask,
screen->format->Gmask,
screen->format->Bmask,
screen->format->Amask
);
SDL_Rect rect;
rect.x = 0;
rect.y = 0;
rect.w = 100;
rect.h = 100;
Uint32 blue = SDL_MapRGB(screen->format, 0, 0, 255);
SDL_FillRect(layer, &rect, blue);
SDL_BlitSurface(screen, NULL, layer, NULL);
SDL_Flip(screen);
SDL_Delay(3000);
return 0;
}
What I get is a black screen, instead of a 100x100 blue rectangle. What I could find by Googling doesn't seem to help me, as those questions either apply to 8bit surfaces (and setting palettes — my bpp is 32 here) or are left unanswered.
So, I would like to know how should I properly blit a generated surface onto a SDL screen.
Edit: I see it was an error in the parameter ordering. The line in question should read
SDL_BlitSurface(layer, NULL, screen, NULL);
Still, I am having trouble to achieve the same effect in my more complex C++ program. I will post the relevant parts of the code here:
main.cpp:
int main(int argc, char** argv)
{
SDLScreen screen(1024, 700, "Hello, SDL!");
SDL_Event event;
SDLMenu menu;
bool shouldQuit = false;
menu.setBounds(200, 100, 200, 600);
menu.setFontName("NK211.otf");
menu.setFontSize(36);
menu.setEffect(sdlteShadowText);
menu.addItem("New game");
menu.addItem("Load game");
menu.addItem("Save game");
menu.addItem("Exit");
menu.render();
while (!shouldQuit)
{
menu.draw(screen.getSurface());
SDL_Flip(screen.getSurface());
SDL_Delay(10);
while (SDL_PollEvent(&event))
{
if (event.type == SDL_QUIT)
{
shouldQuit = true;
}
else if (event.type == SDL_KEYUP)
{
if (event.key.keysym.sym == SDLK_q)
{
shouldQuit = true;
}
}
}
}
}
SDLMenu.cpp:
void
SDLMenu::setSelectionColorRGB(int r, int g, int b)
{
SDL_VideoInfo* info = (SDL_VideoInfo*)SDL_GetVideoInfo();
selectionColor = SDL_MapRGB(info->vfmt, r, g, b);
}
void
SDLMenu::render()
{
SDLText* current = NULL;
SDL_VideoInfo* info = (SDL_VideoInfo*)SDL_GetVideoInfo();
if (!items->empty())
{
current = getItemAt(currentItem);
selectionRect = getItemRect(current);
setSelectionColorRGB(0,0,255);
selectionCanvas = SDL_CreateRGBSurface(SDL_HWSURFACE,
selectionRect->w, selectionRect->h,
info->vfmt->BitsPerPixel,
info->vfmt->Rmask,
info->vfmt->Gmask,
info->vfmt->Bmask,
info->vfmt->Amask);
SDL_FillRect(selectionCanvas, selectionRect, selectionColor);
SDL_SaveBMP(selectionCanvas, "selection.bmp"); // debug
}
for (list<SDLText*>::iterator i = items->begin();
i != items->end(); i++)
{
(*i)->render();
}
}
void
SDLMenu::draw(SDL_Surface* canvas)
{
int currentY = bounds.y;
if (selectionCanvas != NULL)
{
SDL_BlitSurface(selectionCanvas, NULL, canvas, selectionRect);
}
for (list<SDLText*>::iterator i = items->begin();
i != items->end(); i++)
{
(*i)->draw(bounds.x, currentY, canvas);
currentY += fontSize + itemGap;
}
}
SDLScreen.cpp:
SDLScreen::SDLScreen(int w, int h, string t, int d)
: width(w), height(h), depth(d), title(t)
{
SDL_Init(SDL_INIT_EVERYTHING);
SDL_WM_SetCaption(title.c_str(), NULL);
refresh();
}
void
SDLScreen::refresh()
{
screen = SDL_SetVideoMode(width, height, 32, SDL_HWSURFACE);
}
The selection rectangle for the active menu item should be blue, but it shows up in black. The file selection.bmp is also all black.
Edit 2: I found out what created the problem. The selectionRect was set relative to the screen, while the selectionCanvas had the width and height of a particular menu item. So, the filling was done out of bounds of the selectionCanvas. Adding separate SDL_Rect for filling solved the problem.
SDL_Rect fillRect;
fillRect.x = 0;
fillRect.y = 0;
fillRect.w = selectionRect->w;
fillRect.h = selectionRect->h;
SDL_FillRect(selectionCanvas, &fillRect, selectionColor);
// and later...
SDL_BlitSurface(selectionCanvas, NULL, canvas, selectionRect);
You inverted source and destination. To blit on screen, it should be
SDL_BlitSurface(layer, NULL, screen, NULL);
doc for SDL_BlitSurface