Tag Archives: sdl

Savage Vessels

Impressive rogue-like 2D space shooter with pixel-art, physics and hard survival.

Interview with developer KPas

Could you please give a short description of Savage Vessels for those who have never heard of it?

Within fields of asteroids and fragmented freighters you scavenge and
combat against robot vessels. At the same time you have to keep away
from the surrounding void. With your carrier you got into this
threatening area. In order to escape you have to determine your location
repeatedly: leave the carrier, visit some navpoints, land again and move
on. But the robots won’t let you. So you have to arm against them by
gathering and crafting.

The visuals are based on top down pixel-art and a dynamic field of view.
Modern physics provide inertia and collision. Sound fx creates an eerie
atmosphere. It’s a spiritual successor to Teleglitch.

Why did you decide to choose Pascal as a programing language and SDL/SDL2 as a library for this project?

Pascal is my mother tongue. It’s capable of everything I need and I’m
feeling comfortable with it.

SDL is versatile, platform-agnostic and plain.

What do you think is the most interesting Pascal/SDL/SDL2 project out there (besides of your own, of course :-D)?

My nomination for now: DoomRL (https://drl.chaosforge.org/)

Are there any further steps for Savage Vessels and/or are any new projects planned? What will they be?

Savage Vessels is in development and I want to release it on Steam end
of year 2019 or so. You can wishlist it on Steam by the way.

Window and Renderer

Last updated on August 7th, 2018

Every SDL2 program that shall show some graphic output has to have at least one SDL2 window and a SDL2 renderer. The window is the entity that is showing the graphic output and the renderer is the “machine” that is generating the output to be shown in the window. The code to set up a window and a renderer is as follows.

Let’s have closer look at the var clause.

The SDL2 Window

In SDL 2.0 you can create as many windows as you like, and each window is adressed by its PSDL_Window variable. We just need one window for now, let’s call it “sdlWindow1”. It defines the window’s properties, e.g. size, appearance, border, title name and so on. And it holds the content it shows.

Creation of a Window

The creation of a SDL2 window is simple as using the function SDL_CreateWindow(title, x, y, width, height, flags) or more specific:

In our example the window is titled “Window1”, it is located at position x = 50 and y = 50 pixels (relative to your screen). It has a width and height of 500 pixels respecitvly. And we have used the flag SDL_WINDOW_SHOWN. More about these flags later. First let’s get an understanding of the coordinate system in SDL2.

The Coordinate System in SDL 2.0

This rule applies:

The origin from where to count to place a window is always the left upper corner of your screen.

So if you choose (0/0) as coordinates the window’s left upper corner will be placed right at the left upper corner of your screen. The diagram below may help to understand this. You may try SDL_WINDOWPOS_CENTERED for each or both coordinates which will lead to a centered window with respect of the screen. If you choose SDL_WINDOWPOS_UNDEFINED you don’t care for the window’s position.

SDL2 window and coordinates diagram
Creative Commons License This image by https://www.freepascal-meets-sdl.net is licensed under a Creative Commons Attribution 4.0 International License.
The window is placed with respect to the left upper corner of the screen.

SDL 2.0 windows and their properties

Now let’s talk about the flags. They decide for the properties of the window. Look at the following table (source) of possible flags and you may get an idea what they do.

Flag
Description
SDL_WINDOW_FULLSCREENfullscreen window
SDL_WINDOW_FULLSCREEN_DESKTOPfullscreen window at the current desktop resolution
SDL_WINDOW_OPENGLwindow usable with OpenGL context
SDL_WINDOW_SHOWNwindow is visible
SDL_WINDOW_HIDDENwindow is not visible
SDL_WINDOW_BORDERLESSno window decoration
SDL_WINDOW_RESIZABLEwindow can be resized
SDL_WINDOW_MINIMIZEDwindow is minimized
SDL_WINDOW_MAXIMIZEDwindow is maximized
SDL_WINDOW_INPUT_GRABBEDwindow has grabbed input focus
SDL_WINDOW_INPUT_FOCUSwindow has input focus
SDL_WINDOW_MOUSE_FOCUSwindow has mouse focus
SDL_WINDOW_FOREIGNwindow not created by SDL
SDL_WINDOW_ALLOW_HIGHDPIwindow should be created in high-DPI mode if supported (available since SDL 2.0.1)

As you can see, these flags determine different properties of  the window. E.g. SDL_WINDOW_FULLSCREEN will create a fullscreen window and SDL_WINDOW_BORDERLESS will create a borderless window. You may combine several flags by OR (if appropriate). For our purpose SDL_WINDOW_SHOWN is a good choice because we just create a shown window without any further restrictions.

The SDL2 Renderer

In computer graphics rendering means the process of synthesizing the final image on your screen from the individual basic data structures. To draw some content to the window, we need therefore a renderer. The PSDL_Renderer (which we declared in the var clause) is responsible for synthesizing all the content in a window, be it some lines, a flat background, a texture, a 3d object, or whatever. We call our PSDL_Renderer “sdlRenderer”.

Creation of a Renderer

The creation of the renderer is as simple as one function call of SDL_CreateRenderer(window, index, flags) or

First we need the renderer to know where to render the finished/rendered output. That will be “Window1” in our case. Next the shown function asks for a cryptic “index”. Well, each driver which is capable of rendering (e.g. OpenGL, Direct3d, Software,…) is indexed in SDL 2.0. In principle you could choose one specific driver here by choosing the corresponding index. Since we don’t know too much about the drivers at the moment the best choice is -1. -1 means that the first driver which is supporting the chosen flag(s) is chosen. Talking about flags, there are four flags you may choose:

  1. SDL_RENDERER_SOFTWARE
  2. SDL_RENDERER_ACCELERATED
  3. SDL_RENDERER_PRESENTVSYNC
  4. SDL_RENDERER_TARGETTEXTURE

You should always prefer SDL_RENDERER_ACCELERATED because this means the graphics board is responsible for rendering, SDL_RENDERER_SOFTWARE in contrast means, the CPU has to do the rendering. As discussed before for best performance the graphic board is the best choice for rendering/graphic related tasks. SDL_RENDERER_PRESENTVSYNC allows for so called vertical synchronization which means that the display of the rendered image is synchronized with the refresh rate of the monitor. SDL_RENDERER_TARGETTEXTURE allows for rendering to a texture. You may have noticed that none of these flags but 0 was used in the example code. This automatically gives priority to hardware accelerated renderers.

Quick Creation of a Window and a Renderer

Instead of creating the window and the renderer separately as demonstrated, you may use SDL_CreateWindowAndRenderer(width, height, window flags, window pointer pointer, renderer pointer pointer). This has the advantage that you just need one line to set up a window and a renderer, though setting a window title, a window position or specific renderer flags have to be done afterwards if necessary.

Just remove the curly brackets and enclose the “full set up” -part to try it.

This function returns 0 on success and -1 on failure.

Rendering a SDL2 Scene

The actual rendering is achieved by SDL_RenderPresent(renderer). As a sidenote for people coming from SDL 1.2, this is what formerly has been achieved by SDL_Flip().

Freezing (delaying) a running program in SDL 2.0

SDL_Delay(time in milliseconds) is a simple, yet powerful and important procedure to stop the program running for a certain time in milliseconds. 2000 milliseconds are two seconds. This is kind of a twin of Pascal’s Delay procedure.

Clean up the memory in SDL 2.0

Now the final lines of code are discussed. One of the most important rules for sophisticated programming is followed here:

Always clean up the memory on program finish.

For nearly any pointer type generated by SDL 2.0, there is a destroy procedure to remove it from memory. These procedures are comparable to Pascal’s dispose procedure to remove pointer types from memory. Make sure to destroy the objects in the opposite sequence of their generation. We first created a window, then a renderer. So now we go the opposite way, first destroy the renderer and then the window by the procedures SDL_DestroyRenderer(renderer) and SDL_DestroyWindow(window) respectively.

Here we go:

Do not forget to quit SDL2 finally (which we don’t).

That’s it. And now things are going to get really interesting :-).

← previous Chapter | next Chapter →

Viewports

Last updated on August 11th, 2018

SDL2 allows for viewports. Have a look at the following screenshot of a SDL2 game (Battle for Wesnoth).

Modified screenshot of Battle of Wesnoth. (Original source image, as found in the Wesnoth Wiki by Wesnoth developers. Image license: GFDL.)

This is a classical situation to use viewports. The game screen is clearly parted into three distinguished areas. The main screen is the large part left with the mountains and the castles. Then there is the minimap in the right-upper corner. And a statistics overview under the minimap. These areas and the corresponding viewports are highlightened in the following screenshot.

Modified screenshot of Battle of Wesnoth. (Original source image, as found in the Wesnoth Wiki by Wesnoth developers. Image license: GFDL.)

The advantage of viewports is that each of them behaves like an own window, so if you draw to the right outside of viewport 1 in the screenshot above, the texture will just be clipped and there is no overlap into viewport 2 oder 3.

SDL2 window and viewport coordinates diagram
The relation of your screen, a SDL2 window and a viewport within this window are outlined here.

Let’s have a look at the code.

The result will look like this:

Creative Commons License This image by https://www.freepascal-meets-sdl.net is licensed under a Creative Commons Attribution 4.0 International License.
There are three viewports with different background colors and a black dot in the left upper corner.

First we set up some SDL2 rectangles by

“Viewport1” represents the red viewport (left), “Viewport2” the yellow (upper-right) and “Viewport3” the green (lower-right) viewport in the result image.

Notice how we just prepare one “BlackDot” rectangle for a black dot of 3×3 px dimension at location (10/10).

After setting up SDL2, a renderer and a window as known, we start to set up the first (red, left) viewport.

It is simple as that. Use the function SDL_RenderSetViewport(renderer, rectangle pointer) to set up a viewport. This function returns 0 on success or -1 on failure.

After we set up the viewport, we set the draw color by SDL_SetRenderDrawColor(renderer, red, green, blue, alpha) to red (255/0/0/no transparency). Then we use SDL_RenderFillRect(renderer, rectangle pointer) to fill the whole viewport by not specifying a rectangle (nil). Both functions are known from a previous chapter.

Then the color is set to black and a tiny 3×3 rectangle is drawn at location (10/10).

This procedure is repeated for the other two viewports. Notice again, how we use the same rectangle for the black dot though and where it is shown in the result image. The black dot is always drawn at location (10/10) relative to the respective viewport’s location!

As general rule it applies:

The coordinates are always relative to the currently set viewport.

Well, the remaining parts of the code provides nothing new, just the rendering for 2 seconds and some clean up.

Let’s close with some helpful remarks.

No SDL_RenderClear for Viewports!

Do not use SDL_RenderClear(renderer). It will ignore the viewports and clear the whole window with the set drawing color.

Resetting the Viewport

The resetting is done simple by SDL_RenderSetViewport(renderer, nil) as one would expect.

← previous Chapter | next Chapter →

A Custom Mouse Cursor

Last updated on August 8th, 2018

Any good game has a custom mouse cursor. You may think it would be a good idea to have a SDL2 surface or SDL2 texture and render it as any other sprite right at the mouse position to simulate a mouse cursor. DO NOT do this! The mouse cursor is handled separatly from the other rendering to have it smooth and working in critical situations. 

The following code shows how to set up a custom mouse cursor with SDL2 the correct way.

To have a custom mouse cursor we need a variable of type PSDL_Cursor. We call it “sdlMouseCursor” here.

The result looks like this:

Custom Mouse Cursor in SDL2
Creative Commons License This image by https://www.freepascal-meets-sdl.net is licensed under a Creative Commons Attribution 4.0 International License.
The blue cross with the yellow outline is the mouse cursor on the grey canvas/window. 

This is the interesting part of the code with regard to creating a custom mouse cursor. The cursor’s image is defined by a SDL surface. We create the SDL surface as known from a previous chapter from a png image file to “sdlSurface1” here.

The custom mouse cursor is created by the following function, which returns nil on error.

It needs the surface to use as cursor image and two coordinates (hot_x/hot_y) as arguments. They determine where the actual hitting point for this cursor is. Since the example cursor image is of dimensions 16×16 px and represents a cross, the “hot” (hitting) coordiates are (8/8), hence the cross’ center is used for hitting a button or something. In contrast you may imagine a typical arrow shaped mouse cursor, where the hitting point has to be adjusted to be right on the tip of the arrow in the arrow’s image.

If the cursor creation has been successful, it is necessary to set it to be the actual cursor. You may have created many different cursors, so tell SDL which one to use by the following procedure.

The remaining part of the code is just rendering a 500 by 500 pixels window with a grey (128, 128, 128) background that is updated as long as no mouse button has been pressed.

Finally do not forget to free the mouse cursor by SDL_FreeCursor(mouse cursor) as shown.

← previous Chapter | next Chapter →

DoomRL

Short description

DoomRL is based on ID’s famous Doom game. The RL means roguelike.

Showcase and Basic Data

Developer granted permission to use these screenshots.

  • Project name: DoomRL (a.k.a Doom, the Roguelike)
  • Author: Kornel Kisielewicz (Code/Design), Derek Yu (art)
  • Latest version: 0.9.9.7
  • Release date: 2001 (initial version), 19 March 2013 (latest version)
  • Pascal compiler: FPC 3.0
  • SDL Version: 1.2
  • Further libraries: Lua, OpenGL, FMOD
  • License: Donationware
  • Open source: no
  • Official website: http://doom.chaosforge.org

Interview with Kornel Kisielewicz

Why did you decide to choose Pascal as a programming language and SDL as a library for your projects?

Kornel Kisielewicz: Pascal was my first language, and in those days C++ was quite messy. I liked the clean syntax of Pascal and it’s default strong type system. SDL was a no brainer, we wanted a platform independent layer for OpenGL context creation and Input handling, and SDL was the only reasonable choice in that regard at the time.

What do you think is the most interesting Pascal/SDL/SDL2 project out there (besides your own, of course :-D)?

Kornel Kisielewicz: I have been out of touch with the Pascal scene for a long time now.

Are there any new projects planned?

Kornel Kisielewicz: We’re currently working on Jupiter Hell, a spiritual successor to DoomRL, but it’s in full 3d, and written in C++.

Monsterland

Short description

A commercial action shooter with appealing DOS-like appearance by developer Second Variety Games.

Showcase and Basic Data

Developer granted permission to use these screenshots.

  • Project name: Monsterland
  • Author: Second Variety Games
  • Latest version: 1.15
  • Release date: 12/14/2015
  • Pascal compiler: Free Pascal 3.0.0
  • SDL Version: 1.2
  • Further libraries: sdl_image, sdl_mixer
  • License: commercial product
  • Open source: no
  • Official website: none except Steam page: http://store.steampowered.com/app/406920

Interview with Aleksey from Second Variety Games

Could you please give a short description of Monsterland for those who have never heard of it?

Aleksey: Monsterland is a 2D realtime shooter portrayed entirely through ASCII characters. This includes blood, lighting, particles, etc. Its only gameplay mode is a 3-hour story campaign, which has voiceovers, triggers and scripted sequences. The gameplay of Monsterland was heavily influenced by original Doom games (1 and 2).

Why did you decide to choose Pascal as a programming language and SDL as a library for your projects?

Aleksey: Pascal is an underrated, well-rounded programming language. It has good diagnostics and strict syntax, which removes ambiguity from error messages. It also helps that I was first introduced to it in 1992.

SDL was chosen because I’ve also been writing an engine tied to DirectX, and given where Windows is heading, it was a mistake I didn’t want to repeat. SDL 1.2 didn’t have accelerated 2D though, so I had to do it via OpenGL manually.

What do you think is the most interesting Pascal/SDL/SDL2 project out there (besides your own, of course :-D)?

Aleksey: If Dwarf Fortress still used Pascal, I’d name that. Otherwise, DoomRL I guess.

Are there any further steps planned for the Monsterland series? What will they be?

Aleksey: Aw, you flatter, but Monsterland will not be continued.

Are there any new projects planned?

Aleksey: I’m starting to work on a new type of IF (interactive fiction) game. I clearly have an obsession with text visuals.

There’s also the ambitious isometric RPG I’ve been writing in C for years, the “magnum opus”, but it’s too ambitious at the moment, even though a lot of work has been done. I wish I wrote it in Pascal instead – it would’ve been easier to debug.

 

No One's Space

Commercial Free Pascal/SDL Project

The No One’s Space SDL game has been added to the SDL Project page. It is the first commercial title added and Klaus Vor der Landwehr (from Turtle-Games) has kindly provided an interview for us. Feel free to support the game in the greenlight state over at Steam. This game demonstrates that Free Pascal and SDL make games of commercial quality possible.

The installation instruction got extend by an explanation how to install and configure Lazarus.

No One’s Space

Short description

A commercial high quality space shooter by game developer Turtle-Games.

Showcase and Basic Data

Developer granted permission to use these screenshots.

  • Project name: No One’s Space
  • Author: Turtle Games
  • Latest version: Pre-alpha Version
  • First release date: Steam Early Access Release in 2016 (TBA)
  • Compiler: Free Pascal (via Lazarus)
  • SDL Version: 2.0
  • Further libraries: OpenGL, OpenAL, Ogg Vorbis
  • License: Commercial
  • Open source: no
  • Official website: http://www.NoOnesSpace.com

Interview with Klaus Vor der Landwehr from Turtle-Games

Could you please give a short description of No One’s Space for those who have never heard of it?

Klaus Vor der Landwehr: No One’s Space (NOS) is a single-player Retro 2D-Science-Fiction-Shooter with modern physics. It was created as a cross-breed of the classic games Wing Commander I and Star Control II. In NOS, the player experiences a cosmic conflict between four powerful races, taking the role of different heroes. In 54 challenging missions, reaching from manageable duels to large combats, the player controls a variety of vessels and has to go all out to improve his skills to master them all.

Why did you decide to choose Pascal as a programming language and SDL/SDL2 as a library for this project?

Klaus Vor der Landwehr: It wasn’t really a choice. I’m used to Pascal since my school days. I’m a self-taught. I like it.

What do you think is the most interesting Pascal/SDL/SDL2 project out there (besides your own, of course :-D)?

Klaus Vor der Landwehr: Hm, as far as it concerns the programming language, games are rarely tagged. But I’ve seen some impressive stuff right here: Projekt “W” – Phase 2 http://www.saschawillems.de/?page_id=829 (Although I can only assume that it uses SDL).

Are there any further steps for No One’s Space and/or are any new projects planned? What will they be?

Klaus Vor der Landwehr: If the game gets Greenlit, we want to release it on Steam this year (early access) and work further on it.

 

Colorful

Short description

A 2d shooter whose source code is free to study.

Showcase and Basic Data

Developer granted permission to use these screenshots.

  • Project name: Colorful
  • Author: suve
  • Latest version: 1.2
  • First release date: 2012-12-16
  • Compiler: FPC 2.6.2
  • SDL Version: 1.2
  • Further libraries: Originally BASS for audio handling, later replaced with SDL_mixer as to move away from proprietary library; SDL_image; Sour could probably count, too; OpenGL
  • License: zlib w/acknowledgement
  • Open source: Yep. Under zlib, as stated above.
  • Official website: http://svgames.pl

Interview with suve

Could you please give a short description of Colorful for those who have never heard of it?

suve: Colorful is a simple game where the player moves freely around a 2D world, fighting multiple enemies and trying to retrieve colourful artefacts. Originally created in 48h for Ludum Dare, the game is heavily inspired by Hero Core, featuring simplistic graphics and sounds, and a no-game-over approach balancing the overall difficulty level.

Why did you decide to choose Pascal as a programming language and SDL/SDL2 as a library for your projects?

suve: I chose Pascal mostly as it’s the language I’m most proficient and comfortable with. As for SDL, after working with a few different libraries in the past, I’ve found SDL easy to use, but nonetheless really versatile and fitting my needs. The library itself doesn’t really enforce anything on you, so you don’t have to change your habits (much), and the seemingly simplistic API is greatly extended by the supplementary SDL_XYZ libraries.

What do you think is the most interesting Pascal/SDL/SDL2 project out there (besides of your own, of course :-D)?

suve: Supraleiter seems the most awesome of them all, I think. Shame that quite probably I won’t be able to play sit, seeing as I only have an integrated GPU.

Are there any further steps for your projects or any new projects planned? What will they be?

suve: I have two projects underway right now, but one is too early in development and I don’t want to disclose it for fear of not delivering… and the other, for a change, is written in C instead of Pascal. 🙂

 

Alexland

Short description

Alexland is a 2d shooter in a classical style.

Showcase and Basic Data

Developer granted permission to use these screenshots.

  • Project name: Alexland
  • Author: suve & ZbiXs
  • Latest version: 1.3
  • First release date: 2010-01-31
  • Compiler: Free Pascal 2.4.0 (for the 1.3 release)
  • SDL Version: 1.2
  • Further libraries: BASS for audio handling, SDL_image, SDL_ttf, SDL_net
  • License: Back then we didn’t really think about licensing, and seeing how the game contains assets ripped from plenty of places without even keeping track of source… I say it’d be hard for us to claim copyright to anything apart from code and some original graphics (+edits) we created.
  • Open source: Nope. Maybe if there’s a remake one day.
  • Official website: http://svgames.pl

Interview with suve

Could you please give a short description of Alexland for those who have never heard of it?

suve: Born of RPG Maker nostalgia and the hatred for its default graphics set, Alexland is a 2D shooter where the player controls a lone hero in a fight against never-ending hordes of monsters. Featuring 12 weapons to kick ass with, 11 bonuses to enhance the gameplay, 10 monster types to kill, and 60 achievements to unlock, Alexland can provide long hours of mindless, merciless fun. Available in English, Polish, French, German and Russian.

Why did you decide to choose Pascal as a programming language and SDL/SDL2 as a library for your projects?

suve: I chose Pascal mostly as it’s the language I’m most proficient and comfortable with. As for SDL, after working with a few different libraries in the past, I’ve found SDL easy to use, but nonetheless really versatile and fitting my needs. The library itself doesn’t really enforce anything on you, so you don’t have to change your habits (much), and the seemingly simplistic API is greatly extended by the supplementary SDL_XYZ libraries.

What do you think is the most interesting Pascal/SDL/SDL2 project out there (besides of your own, of course :-D)?

suve: Supraleiter seems the most awesome of them all, I think. Shame that quite probably I won’t be able to play sit, seeing as I only have an integrated GPU.

Are there any further steps for your projects or any new projects planned? What will they be?

suve: I have two projects underway right now, but one is too early in development and I don’t want to disclose it for fear of not delivering… and the other, for a change, is written in C instead of Pascal. 🙂