This question concerns drawing a circle in the dos window, not a GUI/form.

I have the function below which plots a point in the 80x25 dos window.

#include < windows.h >
#include < stdio.h >

void plot(int xC, int yC) {
COORD coordinate = {xC,yC};
HANDLE hOutHandle=GetStdHandle(STD_OUTPUT_HANDLE);
SetConsoleCursorPosition(hOutHandle,coordinate);

printf("*");
}

The function above works fine as I have used it in many previous applications. I was wondering how I could use this function to draw a circle-like figure out to the console somehow. I understand that a circle is the collection of all points equidistant from the center but I cannot figure out how to get all the coordinates needed to form this. If anyone has any hints/suggestions or if anyone will explain to me why this would not be possible (if it isn't) please tell me.

Trigonometry or the pythagorean theorum will help.

Ah..I don't know any trigonometry yet and I have no idea how I would apply the pythagorean theorem.

I've been thinking about this for a while..all I've gotten is an inefficient way to produce a mediocre ellipsis-type figure.

"ellipse-type" (ellipsis is a word too, but unrelated)

Applying the pythagorean theorum here isn't very difficult. Draw the problem on paper until you stumble on a right triangle.

- taubz

Oh yeah heh ellipsis=(...). Alright I'll get out the graphing paper and try to figure it out.

You might stumble across another problem, namely that moving n coords along the x-axis dosen't move you the same distance (in pixels) as when you move n coords along the y-axis, as the character cells in the console aren't square. That could be the reason you get an elipsoid (assuming that's the right word :D).

I can't think of any famous Circle drawing algorithms off the top of my head. But a quick search in google finds a fair few essays and references on "drawing a circle on a raster display" or "circle drawing algorithm on a raster display"

ellipsoid is a 3D surface. This time the correct word is "elliptical."

I think these Bresenham line-drawing algorithms will work. Even if they end up not being what I am looking for they are still very interesting..I win either way.

there are plenty of interesting line drawing algorithms, but I can't think of any that can actually be used to easily draw a circle. Perhaps 2 Bezier curves or something.

Then again processing time might be less on a Bezier curve over using Cos/Tan/Sin for drawing a circle.

Yeah thats what I used in my 13h library, the bressenham algos, slightly modified for the .625 aspect ratio (to fix the circles looking like ovals problem)

Basically you now, there are 2 problem's the character cells aren't sqaure, the window itself is not square [at least not when its not full screen].

GetConsoleWindow, a function that is supposed to return the HWND of the console window, doesn't seem to be present on my system. Does anybody else have this problem? I mean, the header files don't have it, and when I added a declaration, the linker gave an error.

How can I get in pixels the size of the part of the window used to display text? Once I have this, I can go about normalizing(is that the word?), the ellipse into a circle.

you might want to look at GetConsoleScreenBufferInfo( HANDLE, PCONSOLE_SCREEN_BUFFER_INFO );

Didn't find GetConsoleWindow() in the SDK-doc's, so I'd guess it dosen't exist. You could try GetActiveWindow(), which gets the window attached to the current process.

MicrosoftReallyShouldHaveThoughtTwiceAboutHowTheyNamedTheirAPIFunctions(); --Oh well, I guess they make sense. I can't think of a better way..

Actually, my docs, the MSDN July 200 CD have the function, but it doens't appear in the code completion of VC++. But GetConsoleScreenBufferInfo seems to return all the sizes in character cells.


Actually, the user can set the size of the font [I think that is the size of the character cell] at the top left corner of the console window. How can the program get at this?

You have to install the mssdk aswell (with updated headers/libs/whatever). I don't really suggest that you do install the mssdk if you're stuff works currently, the only thing it did for me was creating a huge mess from everything.

SetConsoleWindowInfo() maybe. I don't know; I tend to avoid win32 API console stuff, but make sure to check the Console Functions section in the MSDN Platform SDK doc's ;)

and about the long names: that's when a few #def's get really handy.. :D