• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
xDancinpoptartx

[SDL] Help with keyboard input and sprite movement

5 posts in this topic

I'm new to SDL and I was wondering why this keyboard movement wasn't working.
[source lang="cpp"]#include "SDL/SDL.h"
#include <stdbool.h>
//SURFACES/variables
SDL_Surface *background = NULL;
SDL_Surface *buffer = NULL;
SDL_Surface *sprite = NULL;
int y = 250;
int x = 250;
//apply
void apply_surface(int x, int y, SDL_Surface* source, SDL_Surface* destination)
{
SDL_Rect offset;
offset.x = x;
offset.y = y;
SDL_BlitSurface(source, NULL, destination, &offset);
}
//start
int main( int argc, char* args[] )
{
//init
SDL_Init( SDL_INIT_EVERYTHING );

background = SDL_LoadBMP("bg.bmp");
sprite = SDL_LoadBMP("char.bmp");
SDL_SetColorKey(sprite, SDL_SRCCOLORKEY, SDL_MapRGB(sprite->format, 230, 0, 230));
SDL_Event event;
bool fullscreen = false;
bool done = false;
//loops
if (fullscreen == false )
{
buffer = SDL_SetVideoMode(500, 500, 32, SDL_SWSURFACE);
}
//APPNAME
SDL_WM_SetCaption("Game", NULL);
//apply surface/flips
apply_surface(0, 0, background, buffer);
apply_surface(x, y, sprite, buffer);
SDL_Flip(buffer);
//quit
while(!done)
{
while(SDL_PollEvent (&event))
{
switch (event.type)
{
case SDL_QUIT:
{
done = true;
break;
}
case SDL_KEYDOWN:
{
if(event.key.keysym.sym == SDLK_DOWN)
{
y = y+1;
}
}
}
}
}
//END
SDL_FreeSurface(background);
SDL_FreeSurface(sprite);
SDL_Quit();
return 0;
}
[/source]
0

Share this post


Link to post
Share on other sites
You need to draw your scene every frame, not just draw it once in it's first state and then update state, but not drawing.
Place your drawing code inside the while loop (don't have experience with SDL so can't really say if within SDL_PollEvent while or (!done) while but I would say you should put your drawing code inside the !done while.
1

Share this post


Link to post
Share on other sites
[quote name='Dylan_DE' timestamp='1354563279' post='5006735'][code]
apply_surface(x, y, sprite, buffer);
SDL_Flip(buffer);
// ...
while ( !done )
{
// ...
y = y+1;
// ...
}
[/code][/quote]

Think of it this way: Does changing the amount of sugar in a cake recipe change the sugar content for all cakes baked with the same recipe? Of course not; the cake needs to be re-baked every time its recipe changes. Edited by fastcall22
0

Share this post


Link to post
Share on other sites
(First of all, I say sorry for my english)

You just need to draw the scene. Put the apply_surface() function after the SDL_PollEvent while and will work (remember this logic order on games: update logic -> user input -> draw scene to the user).

Another thing is: you want the sprite moving while the key is pressed? or you just want to move him few pixels every time you press the key?
There's 2 ways to do this things:

The way you are doing, you will press the key, then the sprite y will be set to y+1. If you press the key, and keep it pressed, the sprite will not move more than 1 pixel until you press the key again.

The other way is use the function SDL_GetKeyState():


[source lang="cpp"]Uint8* keystate = SDL_GetKeyState(NULL);
if(keystate[SDLK_DOWN])
{
y = y+1;
}[/source]

The SDL_GetKeyState() function get a snapshot of the current keyboard state.
What's the difference? The SDL_KEYDOWN it's an event that just occurs when you press that key, and the way above, it's to check if the current key is pressed, if it's pressed, increments y. (This case will be true until you release the key) Edited by ptrrf
0

Share this post


Link to post
Share on other sites
So where do I put the apply_surface because i put it after the poll event like this
[source lang="cpp"]while (!done)
{
if (SDL_PollEvent(&event))
{
if (event.type == SDL_QUIT)
{
done = true;
}
Uint8* keystate = SDL_GetKeyState(NULL);
if(keystate[SDLK_DOWN])
{
y = y+1;
}
}
apply_surface(x, y, sprite, screen);
}[/source]
0

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0