Drawproc – Like Processing, but in C++

Triangle Strips using drawproc


So, what’s the code look like to create this gem?

#include "drawproc.h"

int x;
int y;
float outsideRadius = 150;
float insideRadius = 100;

void setup() {
	size(640, 360);
	x = width / 2;
	y = height / 2;

void drawStrip()
	int numPoints = int(map(mouseX, 0, width, 6, 60));
	float angle = 0;
	float angleStep = 180.0 / numPoints;

	for (int i = 0; i <= numPoints; i++) {
		float px = x + cos(radians(angle)) * outsideRadius;
		float py = y + sin(radians(angle)) * outsideRadius;
		angle += angleStep;
		vertex(px, py);
		px = x + cos(radians(angle)) * insideRadius;
		py = y + sin(radians(angle)) * insideRadius;
		vertex(px, py);
		angle += angleStep;

void draw() {

If you’ve done any coding in Processing, you can look at the example that inspired this bit of code here: Triangle Strip

What’s notable about it is the similarity to the Java or even the JavaScript version (if processing.js). It takes about a 10 minute conversion to go from Processing to using drawproc. So, what is drawproc?

Drawproc is an application and library which facilitates the creation of interactive graphics. It is the culmination of taking the work from graphicc and encapsulating in such a way that makes it easy to use in multiple situations.

So, how does it work?  Basically, there is the drawproc.exe application.  This application contains a main(), and a primary event loop which takes care of capturing mouse and keyboard events, and issuing “draw()” calls.  Previously (Dyanmic Programming in C) I explained how that dynamic bit of machinery works. All that machinery is at work here with the addition of one more dynamic programming item.

bool InitializeInstance(const char *moduleName)

	// Get pointers to client setup and loop routines
	clientModule = LoadLibrary(moduleName);

	printf("modH: 0x%p\n", clientModule);

	SetupHandler procAddr = (SetupHandler)GetProcAddress(clientModule, "setup");
	printf("proc Address: 0x%p\n", procAddr);

	if (procAddr != NULL) {

	LoopHandler loopAddr = (LoopHandler)GetProcAddress(clientModule, "draw");
	printf("loop Addr: 0x%p\n", loopAddr);

	if (loopAddr != NULL) {

	if ((procAddr == nullptr) && (loopAddr == nullptr))
		return false;

	gClock = dproc_clock_new();

	return true;

When invoking drawproc, you give a name of a module, which is a .dll file compiled against the .exe. Typical execution looks like this:

c:\tools>drawproc trianglestrip.dll

That ‘trianglestrip.dll’ is passed along to the InitializeInstance() call, the module is loaded, and the ‘setup()’ and ‘draw()’ functions are looked for. If neither of them is found, or the .dll doesn’t load, then the program quits. At this point, everything is the same as if you had linked the drawing module into the drawproc.exe program directly. The advantage is you have a simple small (~200K for debug version) executable (drawproc.exe) which is very slow changing. Then you have the modules, which can be numerous, and dynamic. You can create modules independently of the drawproc.exe and run as you wish. You could even write a single module which loads .lua, or any other embedded scripting environment, and write your code using that scripting language instead.

How do you create these modules? Well, you just write your code, make reference to the header files within drawproc, and use drawproc.lib as the library reference. All the relevant symbols within drawproc are exported, so this just works. At the end of the day, the drawproc.exe looks just like any other .dll that might be out there.

In case you’re still reading, here’s another picture.

SineConsoleBanate CAD 2011

This one is interesting because it’s actually an animation (SineConsole).  A few years back, when I was experimenting with BanateCAD, I had done something similar, all in Lua Banate CAD 2011.

Why bother with all this though?  Why C? What’s the point?  I had this interesting conversation last week with a co-worker.  We were discussing whether people who are coming into becoming software programmers would be better served by learning C#, or C/C++.  I think my answer was C#, simply because it seems more in fashion and more applicable to other dynamic languages than does C/C++.  But, here we’re doing a lot of ‘dynamic’ with standard C/C++.  Really the answer to that question is “you will need to learn and use many languages, frameworks, and tools in your software development.  Learning some C will likely serve you well, but be prepared to learn many different things.’

drawproc being written in C/C++ is great because it makes programming graphics fairly simple (because of the Processing mimicry).  Using the Processing API makes the graphics stuff really easy.  At the same time, since it’s written in C/C++, gaining access to the lowest level stuff of the platform is really easy as well.  For example, integrating with the Microsoft Kinect sensor is as easy as just using the Microsoft Provided SDK directly.  No shim, no translation layer, no ‘binding’ to get in the way.  That’s a very good thing.  Also, as time goes on, doing the accelerated this and that, throwing in networking and the like will be a relative no brainer.

So, there you have it.  drawproc is a new standalone tool which can be used for fiddling about with graphics.  For those who are into such things, it’s a nice tool to play with.


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