130 lines
3.5 KiB
Markdown
130 lines
3.5 KiB
Markdown
---
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title: 3DS Programming - Hello World
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description: A guide to creating a simple Hello, World program for the 3DS. (Old)
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date: 2025-01-01
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tags: ['3ds', 'programming', 'c', 'devkitpro', 'old']
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next: old3ds_romfs.md
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---
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# Hello, World!
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::alert{type="warning"}
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This guide of mine is old - Like 3 years old at the time of posting. I prefer to keep it up, but I don't think it very highly - It should still work though.
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I might make a new one in the future.
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I'm doing some alterations at least to make it more readable.
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It doesn't teach why things are done very well is my primary issue with it.
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::
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'Hello, World!' is a very simple program used for checking a program's build system, and showing its basic syntax.
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We should do both before going forward. You should have your project set up for this.
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And if you are using VSCode, I would recommend you get the include paths set up.
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## Begin coding
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Start by including 'stdio.h' (or 'cstdio'!) and '3ds.h'.
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A quick explanation of '3ds.h'
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'3ds.h' is the file containing references to all the VITAL things we can use to program on the system.
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It does not include many features, such as (And certainly not limited to) rendering capabilities, aside from running the console)
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## Main loop
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Start by setting up a main function as usual for C/C++.
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To initialize the graphics, we need to run gfxInitDefault().
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To initialize the console, we need to run consoleInit([SCREEN HERE], NULL).
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Replace '[SCREEN HERE]' with either GFX_TOP or GFX_BOTTOM, depending on what screen you want.
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At this point, the code should look something like this:
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<!-- Note: I originally used images for these, but... Why did I do that? -->
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```c
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#include <stdio.h>
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#include <3ds.h>
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int main() {
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// Initialize the console
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gfxInitDefault();
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consoleInit(GFX_BOTTOM, NULL);
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return 0;
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}
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```
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As the console is now ready, you can now print to the screen. You can use puts(), printf(), std::cout, etc.
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If we try and run it now, it should immediately close itself, as there is no main loop.
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To create a main loop, we create a while loop with aptMainLoop() as its argument:
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```c
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// Initialize the console
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// ...
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/// Main loop
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while(aptMainLoop()) {
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// Code here
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}
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```
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This will loop infinitely until the user closes the program.
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## Input
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Okay, so we now have a main loop... How do we exit back to the Homebrew Launcher?
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Simple. We can scan for input, and break if it detects a button, in this case START, being pressed.
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We can scan for input with hidScanInput(), and get which keys are down with hidKeysDown() like so:
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```c
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// Main loop
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while(aptMainLoop()) {
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// Scan for input
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hidScanInput();
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u32 kDown = hidKeysDown();
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}
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```
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Every button is mapped to a different bit on the unsigned 32-bit integer.
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We can get specific keys via an AND operation between the integer and the desired key:
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```c
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// Main loop
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while(aptMainLoop()) {
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// Scan for input
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hidScanInput();
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u32 kDown = hidKeysDown();
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// Break if START is pressed
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if(kDown & KEY_START) break;
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}
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```
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## Wrapping up
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We can add V-Sync with gspWaitForVBlank(), which may help if you want that and don't want to draw anything aside from the console. You can disregard this if you want:
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```c
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// Main loop
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while(aptMainLoop()) {
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// Scan for input
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// ...
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// Break if START is pressed
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// ...
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// Wait for V-Blank
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gspWaitForVBlank();
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}
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```
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And we are done. You can run the program, and get the words 'Hello, World!' printed on the screen:
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