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[WIP] Improve knightos/display.h #23

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[WIP] Improve knightos/display.h #23

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468b755
Added a function to display signed integers
aviallon Jun 6, 2020
a6e584f
Added a draw_float function (implemented in C)
aviallon Jun 6, 2020
a35754c
Use log10u from math.h
aviallon Jun 14, 2020
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14 changes: 13 additions & 1 deletion include/knightos/display.h
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Original file line number Diff line number Diff line change
Expand Up @@ -97,8 +97,20 @@ void draw_short(SCREEN *screen, unsigned char x, unsigned char y, unsigned short
**/
void draw_byte(SCREEN *screen, unsigned char x, unsigned char y, unsigned char value);

/*.*
/**
* Draws a signed short at x, y
**/
void draw_signed(SCREEN *screen, unsigned char x, unsigned char y, signed short value);

/**
* Draws a float at x,y
**/

void draw_float(SCREEN* screen, unsigned char x, unsigned char y, float value);

/**
* Draws a long at x, y
* NYI
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TODO is better, it's more commonly used

**/
void draw_long(SCREEN *screen, unsigned char x, unsigned char y, unsigned long value);

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40 changes: 40 additions & 0 deletions src/knightos/display.c
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Expand Up @@ -330,6 +330,46 @@ void draw_short(SCREEN *screen, unsigned char x, unsigned char y, unsigned short
screen; x; y; value;
}

void draw_signed(SCREEN* screen, unsigned char x, unsigned char y, signed short value) {
if(value < 0){
draw_char(screen, x, y, '-');
x += 4;
value = -value;
}
draw_short(screen, x, y, value);
return;
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Why the explicit return?

}

void draw_float(SCREEN* screen, unsigned char x, unsigned char y, float value){
/* Implementation is weird and slow because of non-working snprintf. Indeed, %f format strings are not yet implemented */
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@aviallon what was wrong with snprintf?

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%f doesn't work at all (it's ignored). I don't know if it is standard, but every libc I know supports it. And it really is useful.

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@MaxLeiter MaxLeiter Jun 6, 2020 •
edited
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I can't remember why we didn't implement %f, and there's probably a good reason, but you may want to experiment with https://github.com/KnightOS/libc/blob/master/src/format.c

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Worst case, I'd like to see %f support using this function as a base.

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Actually, this function has a major issue :
it does not support floats whose integer part is greater than INT_MAX...
In order to have full float support, I would have to go char by char... which may be even slower 😞

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Let me know when this PR is done.

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Yup, I will do. If you have any idea on a fast implementation for that, I'm all ears 😝

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First idea: don't worry about fast. It can be sped up later if we need to.

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Let me know when this is ready for another review :)

unsigned int integer_part;
unsigned int frac_part;
unsigned int integer_part_len;
bool sgn = (value < 0);


value = sgn ? -value : value;

integer_part = (unsigned int)value;
frac_part = ((value - (float)integer_part)*10000);

integer_part_len = (log10u(integer_part)) + 1;

if(sgn){
draw_char(screen, x, y, '-');
x += 4;
}

draw_short(screen, x, y, integer_part);
x += integer_part_len*4;
draw_char(screen, x, y, '.');

x += 4;
draw_short(screen, x, y, frac_part);

return;
}

void invert_pixel(SCREEN *screen, char x, char y) {
__asm
POP BC ; return
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