Re: Proper C Pointer Binding
Thanks for the suggestions! I think then I will stay with
a wrapping struct. How would I make the extern C functions
invisible for other sources?
extern (C) c_ulong loadFont(char * path);
extern (C) void render(c_ulong font, char * text);
extern (C) void destroyFont(c_ulong font);
struct Font {
private:
c_ulong ptr;
public:
this(string path) {
ptr = loadFont(path.toStringz());
}
void render(string text) {
render(ptr, text.toStringz());
}
~this() {
destroyFont(ptr);
}
}
When released as a library I would simply not put them
in the di Files, but I do not really want to use di-s for
developing the lib, but generate them for release.
Can I declare these extern C functions inline the
methods using it?
Re: Proper C Pointer Binding
On Saturday, 5 April 2014 at 13:55:27 UTC, Róbert László Páli
wrote:
When released as a library I would simply not put them
in the di Files, but I do not really want to use di-s for
developing the lib, but generate them for release.
Can I declare these extern C functions inline the
methods using it?
Unfortunately not, because they then their names get mangled
incorrectly.
Maybe DMD should be changed to not output private declarations,
if they are not needed (i.e. don't affect struct layout, for
example), then you can just declare them in a `private { }` block.
Proper C Pointer Binding
I am programming a new GUI widget library based on OpenGL for D.
For that I manually bind the used OpenGL functions to D and create
an abstraction layer to draw things, boxes, texts, shapes, etc.
http://palaes.rudanium.org/HueApp/intro.php
The thing compiles nicely with SDL, FreeType, FTGL. But
for the text drawing I use some pretty lame binding currently.
It is a fresh part of the code and want to do it properly:
C Code:
unsigned long loadFont(char * path) {
FTGLfont * font = FTGLloadFont(path);
return (unsigned long) font;
}
void drawText(unsigned long font, unsigned size, char * text) {
// do the text drawing here
}
void destroyFont(unsigned long font) {
FTGLdestroyFont((FTGLfont * ) font);
}
D Code:
extern (C) ulong loadFont(char * path);
extern (C) void destroyFont(ulong font);
void main() {
// init screen and OpenGL setup
auto font = loadFont(cast (char * ) Arial.TTF);
scope (exit) destroyFont(font);
// draw some text
// close OpenGL and SDL with some second delay
}
This works properly, and long is surely large enough to hold
a pointer in it, I could use sizet, I know that would be better.
My problem is that auto font here is an ulong. Could that be
wrapped into a type Font so that it only accepts assignment
from other Font type but no insecure numeric caluclations
and make the loadFont return that Font type, and other
methods use Font as arguments?
Re: Proper C Pointer Binding
void main() {
// init screen and OpenGL setup
auto font = loadFont(cast (char * ) Arial.TTF);
scope (exit) destroyFont(font);
// draw some text
// close OpenGL and SDL with some second delay
}
Also I am not sure about the string casting to char * here.
I have been told that literals are 0 terminated, but strings
usually are not. Should I in your opinion create a wrapping
function in D that does convert the string to a proper
char * value? And how would I do that?
Thanks in advance for all the help!
Róbert László Páli
Re: Proper C Pointer Binding
R:
void main() {
// init screen and OpenGL setup
auto font = loadFont(cast (char * ) Arial.TTF);
scope (exit) destroyFont(font);
// draw some text
// close OpenGL and SDL with some second delay
}
Also I am not sure about the string casting to char * here.
I have been told that literals are 0 terminated, but strings
usually are not. Should I in your opinion create a wrapping
function in D that does convert the string to a proper
char * value? And how would I do that?
Generally try to avoid casts as much as possible in D 2.066,
because they sometimes are wrong and the compiler is not catching
your mistakes.
Take a look at the toStringz function in Phobos.
There is also the .ptr attribite of dynamic arrays.
But a D string is (immutable char)[], so its ptr is (immutable
char)*.
Bye,
bearophile
Re: Proper C Pointer Binding
On 3/26/2014 6:51 PM, Róbert László Páli wrote:
I am programming a new GUI widget library based on OpenGL for D.
For that I manually bind the used OpenGL functions to D and create
an abstraction layer to draw things, boxes, texts, shapes, etc.
http://palaes.rudanium.org/HueApp/intro.php
The thing compiles nicely with SDL, FreeType, FTGL. But
for the text drawing I use some pretty lame binding currently.
It is a fresh part of the code and want to do it properly:
C Code:
unsigned long loadFont(char * path) {
FTGLfont * font = FTGLloadFont(path);
return (unsigned long) font;
}
void drawText(unsigned long font, unsigned size, char * text) {
// do the text drawing here
}
void destroyFont(unsigned long font) {
FTGLdestroyFont((FTGLfont * ) font);
}
D Code:
extern (C) ulong loadFont(char * path);
extern (C) void destroyFont(ulong font);
void main() {
// init screen and OpenGL setup
auto font = loadFont(cast (char * ) Arial.TTF);
scope (exit) destroyFont(font);
// draw some text
// close OpenGL and SDL with some second delay
}
This works properly, and long is surely large enough to hold
a pointer in it, I could use sizet, I know that would be better.
A big gaping hole here is that longs in C can be 32-bit or 64-bit
depending on the compiler and platform. Any time you want to bind to
anything using longs in C, you should import core.stdc.config and use
the c_long and c_ulong types.
Re: Proper C Pointer Binding
On Wednesday, 26 March 2014 at 09:51:04 UTC, Róbert László Páli
wrote:
I am programming a new GUI widget library based on OpenGL for D.
For that I manually bind the used OpenGL functions to D and
create
an abstraction layer to draw things, boxes, texts, shapes, etc.
http://palaes.rudanium.org/HueApp/intro.php
The thing compiles nicely with SDL, FreeType, FTGL. But
for the text drawing I use some pretty lame binding currently.
It is a fresh part of the code and want to do it properly:
C Code:
unsigned long loadFont(char * path) {
FTGLfont * font = FTGLloadFont(path);
return (unsigned long) font;
}
void drawText(unsigned long font, unsigned size, char * text) {
// do the text drawing here
}
void destroyFont(unsigned long font) {
FTGLdestroyFont((FTGLfont * ) font);
}
D Code:
extern (C) ulong loadFont(char * path);
extern (C) void destroyFont(ulong font);
void main() {
// init screen and OpenGL setup
auto font = loadFont(cast (char * ) Arial.TTF);
scope (exit) destroyFont(font);
// draw some text
// close OpenGL and SDL with some second delay
}
This works properly, and long is surely large enough to hold
a pointer in it, I could use sizet, I know that would be better.
My problem is that auto font here is an ulong. Could that be
wrapped into a type Font so that it only accepts assignment
from other Font type but no insecure numeric caluclations
and make the loadFont return that Font type, and other
methods use Font as arguments?
You probably want something like this:
struct Font {
static Font opCall(string path) {
Font f;
f.fptr = loadFont(path.toStringz());
return s;
}
c_ulong fptr;
}
use it like this:
Font arial = Arial.TTF;
when pasing font to extern functionst that accept ulong use
arial.fptr, in your (D) functions use Font.
Re: Proper C Pointer Binding
static Font opCall(string path) {
Font f;
f.fptr = loadFont(path.toStringz());
return s;
}
That should be return f; of course.
