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Posts about cobrapy

CobraPy? CobraPew! Pew!

It has been a week and I had not re­al­ly touched Co­braPy my 80s-style python en­vi­ronem­nt at al­l. UN­TIL YES­TER­DAY.

So, how is it look­ing now? Like this, us­ing as­sets from the AWE­SOME ken­ney.nl:

I have added:

  • Sup­port for mu­sic (y­ou are lis­ten­ing to 80616-lunchip.xm)
  • Sup­port for sounds
  • Some im­prove­ments to the sprite en­gine (reusing tex­tures and such)
  • Bet­ter key­board sup­port, or at least one that's more use­ful for games
  • Fixed a bunch of bugs
  • Added col­li­sion de­tec­tion (did not make it to the video but it's there)

So let's go over the whole source code for that "game" and see how it work­s? Keep in mind that this code will look bizarre for your stan­dard Python pro­gram­mer be­cause it's de­lib­er­ate­ly done in a ... "ba­sic" style? Even in a BA­SIC style. Which means it aims to be more "struc­tured pro­gram­ming" than what you are used to see­ing.

Al­so, there are no guar­an­tees that any of the APIs ex­posed will even ex­ist to­mor­row, since this is still in a pro­to­typ­ing phase and things will change.

import time

load_sprite("player", "assets/PNG/playerShip3_orange.png")
x = 100
y = 500
step = 3
move_sprite("player", x, y)

We cre­at­ed the in­trepid play­er's ship, and put it "some­where". Sprites are iden­ti­fied by a name. All sprite op­er­a­tions will use that name to know what sprite should be af­fect­ed.

# A fleet of bad ships
fleet = [
    [f"enemy-1-{x}" for x in range(7)],
    [f"enemy-2-{x}" for x in range(7)],
    [f"enemy-3-{x}" for x in range(7)],
    [f"enemy-4-{x}" for x in range(7)],
]

for invader in fleet[0]:
    load_sprite(invader, "assets/PNG/Enemies/enemyBlack1.png")
for invader in fleet[1]:
    load_sprite(invader, "assets/PNG/Enemies/enemyBlue2.png")
for invader in fleet[2]:
    load_sprite(invader, "assets/PNG/Enemies/enemyGreen3.png")
for invader in fleet[3]:
    load_sprite(invader, "assets/PNG/Enemies/enemyRed4.png")

Again, just a few ships with dif­fer­ent look­s.


def move_fleet(x, y):
    """Move fleet so the left-top alien is in position x, y"""
    for inv_y, row in enumerate(fleet):
        for inv_x, invader in enumerate(row):
            move_sprite(invader, x + 90 * inv_x, y + 90 * inv_y)


fleet_x = 50
fleet_y = 50
fleet_step_x = 1
fleet_step_y = 5

A func­tion to move the fleet as a whole, and some in­fo about it, lo­ca­tion and speed.

load_sprite("laser", "assets/PNG/Lasers/laserBlue01.png")
load_sound("laser", "assets/Audio/laserRetro_004.ogg")
laser_last_shot = time.time()
laser_x = -100
laser_y = 0


def shoot():
    global laser_x, laser_y, x, y, laser_last_shot
    play_sound("laser")
    laser_x = x
    laser_y = y
    laser_last_shot = time.time()

Same for our lonely bullet, but we have a couple of new things. With load_sound we load into the program a sound (surprise!) and with play_sound it's played. Just like sprites, they are identified by name.

We keep track of when we shoot be­cause this is a ship, not a ma­chine­gun, Jim!

def check_hit():
    global laser_last_shot
    t1 = time.time()
    global laser_x
    for row in fleet:
        for invader in row:
            if check_collision("laser", invader):
                laser_x = -100
                laser_last_shot = 0

Col­li­sion de­tec­tion! If the bul­let hits an in­vad­er ... well, we can't make it ex­plode yet, but we move the bul­let out and al­low the us­er to shoot again, at least.

load_music_stream("background", "80616-lunchip.xm")
play_music_stream("background")

Just load and play a nice chip­tune! As usu­al, mu­sic is iden­ti­fied by a la­bel, so we can have more than one and play the one we wan­t.

def gameloop():
    global x, fleet_x, fleet_y, fleet_step_x, fleet_step_y, laser_y

The gameloop function is special. Whatever you put here CobraPy will try to run it 60 times a second. No faster, maybe slower if your gameloop takes too long. So this is where you do things like update the screen and interact with the user. You know ... a game loop.

    if is_pressed(114) and x < 720:  # right arrow
        x += step
    if is_pressed(113) and x > 0:  # left arrow
        x -= step
    if is_pressed(38): # a
        if time.time() - laser_last_shot > 1:
            shoot()

User interaction! Basically is_pressed takes a key identifier (nice constants coming soonish) and tells you if it's pressed or not. So, if right-arrow is pressed, increase x (within limits), if left-arrow is, decrease it (within limits). If "a" is pressed and you have not shot for a second, shoot.

    move_sprite("player", x, 500)

Well, that's why we in­creased / de­creased it, right?

    fleet_x += fleet_step_x
    move_fleet(fleet_x, fleet_y)
    if fleet_x < 50 or fleet_x > 150:
        fleet_step_x = -fleet_step_x
        fleet_y += fleet_step_y

The fleet moves to the right, then to the left, and at ev­ery turn, down. Does it re­mind you of any game you've seen?

    laser_y -= step
    move_sprite("laser", laser_x, laser_y)

Bul­let go up.

    check_hit()

En­e­my go boom. Even­tu­al­ly.

CobraPy: a group of minimum viable things

A group of crows is called a mur­der of crows. A group of hares is called a coun­cil of hares.

In fac­t, that's just a bunch of things vic­to­ri­ans made up be­cause they had lots of free time and they had­n't in­vent­ed the In­ter­net yet, and most of those were nev­er ac­tu­al­ly wide­ly used.

BUT what's the name for a group of things that are in a min­i­mal­ly vi­able state?

Well, Co­braPy, my 80s-style python pro­gram­ming en­vi­ron­ment is slow­ly crawl­ing in­to be­com­ing one of those.

Of the com­po­nents I wan­t, I have one of each. They all suck but they suck in the same way a 3 year old play­ing pool suck­s. He will not be great but it's still cool.

  • I am go­ing to punt in hav­ing the ed­i­tor I want be­cause I can make do with Mi­cro for the time be­ing (works flaw­less­ly in my ter­mi­nal!)
  • The RE­PL is not great but it can do what it can do
  • The graph­ics serv­er works (although its API is lim­it­ed to draw­ing cir­cles)
  • The ter­mi­nal is bet­ter than ex­pect­ed, could re­al­ly be used as a dai­ly driv­er ex­cept for some pro­grams re­al­ly not lik­ing it.

And al­so, I have com­bined all the things so that you can start a win­dow that:

  • Is a ter­mi­nal
  • That runs the re­pl
  • Where you can use the graph­ics API
  • And it dis­plays in the same win­dow

What nex­t? I could think about what nex­t. Or ...

I could try to write a sim­ple game and im­ple­ment all the things that don't ex­ist.

Ex­cept for in­put. I need to solve how to do in­put. You see, the user-cre­at­ed pro­grams don't run in the same space as the win­dow. That's why we have a graph­ics pro­to­col. The pro­gram puts things in it, the win­dow reads them and graph­ics ap­pear.

But in­put needs to go the oth­er way around. So I need to add a sec­ond pro­to­col to send back events and it needs to be pret­ty fast. I don't think it's go­ing to be a prob­lem (us­er ac­tions hap­pen on­ly once ev­ery few dozens of mil­lisec­ond­s!) but af­ter that's done?

It's go­ing to be time for ...

Or ac­tu­al­ly, to fail at im­ple­ment­ing it, but im­prov­ing the plat­form in the process. Be­cause fail­ure is what im­prove­ments are made of.

CobraPy: bits and pieces

As it hap­pens in ear­ly stages in fun prod­uct­s, progress in Co­braPy has been both faster and slow­er than ex­pect­ed.

In the past few days a num­ber of things hap­pened:

I made that terminal a whole lot nicer

I al­ready had a ter­mi­nal but I fixed a num­ber of things.

  • The key­board han­dling is much bet­ter, it now rec­og­nizes pret­ty much all keys, which is al­ways a nice thing.
  • It sor­ta sup­ports things like "á" via mod­e-switch (no dead­keys sup­port prob­a­bly ev­er)
  • It has 24-bit col­or sup­port! I did­n't know ter­mi­nals could sup­port that kind of thing!

I added a graphics protocol to it!

Ter­mi­nals with graph­ics sup­port have a very long tra­di­tion. This is a VT55, re­leased in 1977 dis­play­ing graph­ic­s:

How did it work? Well you can read the pro­gram­mer's man­u­al if you wan­t, but ba­si­cal­ly you sent a con­trol se­quence that put it in "graph­ics mod­e" and then sent com­mands de­scrib­ing what to dis­play.

Sim­i­lar ideas with dif­fer­ent pro­to­col de­tails were used in many dif­fer­ent fu­ture ter­mi­nal­s, in­clud­ing ReG­IS graph­ics and Tek­tron­ix vec­tor graph­ics and you could even trace this all the way to a cur­rent Lin­ux desk­top's X11 graph­ic­s.

So, what did I do? Not that, ex­act­ly. I am cre­at­ing a side-chan­nel as a sort-of-R­PC where you send se­ri­al­ized python method names and ar­gu­ments.

I wrote a Python REPL

I want­ed an in­ter­ac­tive mode that was slight­ly friend­lier than Python comes with, but not some­thing over­whelm­ing and pow­er­ful like IPython or BPython.

I did some re­search, and found pt­python which is pret­ty awe­some, but still a bit too much awe­some.

And then I start­ed on a much, much lamer ver­sion of it. Still em­bri­on­ic, but it does work. I have some plans for it.

I learned a lot more about Raylib

All the graph­ics and ba­si­cal­ly ev­ery­thing you see in this project is done us­ing the awe­some raylib and a home­grown CF­FI bind­ing for it. I was not us­ing it right, now I use it bet­ter, and things that took sev­er­al hun­dredth sec­onds now take a few dozen mi­crosec­ond­s.

I integrated the whole thing, sorta

So, I in­te­grat­ed it enough that you can start the ter­mi­nal, launch the RE­PL in it, and use the graph­ics pro­to­col to draw some­thing!

What next

Now comes a round of in­te­gra­tion, cleanup and op­ti­miza­tion.

  • Work­ing code needs to be re­or­ga­nized
  • The ter­mi­nal us­es 66% of a CPU core, which is not ac­cept­able, but there's tons of low hang­ing fruit there.
  • Graph­ics pro­to­col needs to be able to do more things so it's in­ter­est­ing

Af­ter that will come a new round of fea­ture work, and so on for the next ... 10 years? If it goes well?

Here, have a terminal

Co­braPy is in large part about rein­vent­ing wheel­s. We do, af­ter al­l, have per­fect­ly fine 80s-style de­vel­op­ment en­vi­ron­ments in the mil­lions of 80s com­put­ers float­ing around, as well as em­u­la­tors, things like the Maximite and so on.

How­ev­er, I on­ly want to rein­vent fun wheel­s, so I am not do­ing a text ed­i­tor. And prob­a­bly gonna hack a ter­mi­nal-based RE­PL. And there's no way I am do­ing my own wifi con­fig tool (again) so, I should have a reg­u­lar, or­di­nary ter­mi­nal.

But the things I want that ter­mi­nal to do are ... un­usu­al, like raster graph­ic­s, and sprites. So ... why not do my own ter­mi­nal for this?

It's not the first ter­mi­nal I write! I wrote a dumb ter­mi­nal em­u­la­tor around 1998 and I wrote a very ba­sic one us­ing python, pygame and pyte a few months ago. It's on video!

But this time I want­ed a bet­ter one, since I want this to look good. So I went and wrote one.

It us­es many 3rd par­ty things, be­cause life is short.

  • Pyte for all the nit­ty grit­ty of ter­mi­nal em­u­la­tion
  • raylib for all the graph­ics
  • mon­oid is the font
  • This page helped me with things like "what was the es­cape code for left­????"

And it looks this nice:

Yes, NICE, Stu­ar­t.

Side Projects have Projects as Side Effects

I went and did a thing. But why, why?

When I start­ed play­ing with the idea of do­ing a sort-of-retro-80s-pro­gram­ming-en­vi­ron­ment called Co­braPy I sus­pect­ed one of the prob­lems would be find­ing a graph­ics li­brary that did what I want­ed and had good per­for­mance.

I have used PyGame a lit­tle in the past but nev­er liked it too much, so I tried Py­glet and it was work­ing great ... un­til I tried to add some­thing as sim­ple as a wid­get to en­ter tex­t. It does­n't re­al­ly do wid­get­s, for that you ap­par­ent­ly use glooey

But glooey is ... I don't like it. And then I ran into a bug where you can either clean the contents of an EditableLabel and set it to focused without it crashing deep in its bowels. I worked around it by using fake mouse events to focus. And then noticed you can't type a double quote in one of those widgets. So, I got pissed.

It lit­er­al­ly took me less time to find a nice C game li­brary, read a tu­to­ri­al on CF­FI, do min­i­mal ed­its to its head­er file, learn how to use in­voke and write my first pro­gram us­ing it than I wast­ed chas­ing that glooey bug.

And now, the ques­tion­s:

  • Does it work well? How could I know, I on­ly wrote the bind­ing, I have not used it yet!
  • Will I main­tain it? I don't think it re­quires much main­tain­ing.
  • Will I re­lease it? Maybe. It's here, mixed up with oth­er stuff

... aaaaand some­one else had al­ready done it. http­s://pyp­i.org/pro­jec­t/raylib/ But that's raylib 2.6, cur­rent is 3.0 :-)


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