main.c (d476d64) - iv · DKL9 GitList

main.c

/* iv/main.c - see README */

#include <libgen.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "SDL2/SDL.h"
#include "SDL2/SDL_image.h"

#define TWICE(x) for (int j = 0; j < 2; j++) { x; }
#define ZSH(a, b) ((a) * powf(2, b))
#define CLAMP(a, x, b) ((x) < (a) ? (a) : ((x) > (b) ? (b) : (x)))
#define APS 6
#define FPS 60
#define FRAMETIME (1000 / FPS)
#define DZDS 0.25

struct ViewState {
    SDL_Texture* tex;
    /* image dimensions */
    unsigned int idim[2];
    /* zoom level */
    float zoom;
    /* pan position (centre of image) */
    int pan[2];
};

/* if cond is true, exit the program as a failure,
with msg as the message, along with the SDL error, if showsdl is true */
void cfail(const int cond, const char* msg, const int showsdl) {
    if (cond) {
        fprintf(stderr, "iv: failed to %s\n", msg);
        if (showsdl) {
            fprintf(stderr, "SDL: %s\n", SDL_GetError());
        }
        exit(EXIT_FAILURE);
    }
}

/* make alpha checker pattern */
SDL_Texture* checker(SDL_Renderer* ren, int w, int h) {
    SDL_Texture* tex = SDL_CreateTexture(
        ren,
        SDL_PIXELFORMAT_RGBA8888,
        SDL_TEXTUREACCESS_STREAMING,
        w, h
    );
    cfail(!tex, "make background texture", 1);

void* pixels;
    int pitch;
    cfail(
        SDL_LockTexture(tex, NULL, &pixels, &pitch),
        "lock background texture", 1
    );

for (int y = 0; y < h; ++y) {
        Uint32* row = (Uint32*)((Uint8*)pixels + y * pitch);
        for (int x = 0; x < w; ++x) {
            row[x] = 0xB0B0B0FF + 0x40404000 * (x + y & 1);
        }
    }

SDL_UnlockTexture(tex);
    return tex;
}

/* process command-line options, setting pointed strings */
void handleargs(int argc, char** argv, char** title) {
    int oc;
    while ((oc = getopt(argc, argv, "ht:")) != -1) {
        switch (oc) {
            case 'h':
                printf(
                    "iv - image viewer\n"
                    "\nUsage: iv [-t TITLE] FILES\n"
                    "\n-t TITLE sets a custom window title\n"
                    "\nClick and drag to pan\n"
                    "Scroll to zoom\n"
                    "Right-click or space key to centre image\n"
                    "Middle-click to get coordinates at cursor\n"
                    "Arrow keys to move between images in the list\n"
                    "version 1.8-dev\n"
                );
                exit(EXIT_SUCCESS);
            case 't':
                *title = optarg;
                break;
            case ':':
            case '?':
                cfail(1, "parse options", 0);
        }
    }
}

/* load images from arguments */
SDL_Surface** loadimages(char** argv, const int fc) {
    SDL_Surface** isurf = calloc(fc, sizeof (SDL_Surface*));
    for (int i = 0; i < fc; i++) {
        const char* fname = argv[optind + i];
        SDL_RWops* ir;
        if (!strcmp(fname, "-")) {
            ir = SDL_RWFromFP(stdin, 0);
        } else {
            ir = SDL_RWFromFile(fname, "r");
        }
        cfail(!ir, "open file", 1);
        isurf[i] = IMG_Load_RW(ir, 1);
        cfail(!isurf[i], "load image", 1);
    }
    return isurf;
}

void updatetitle(SDL_Window* window, const char* ct, char** title, const char* fname, const struct ViewState vs) {
    if (!ct) {
        free(*title);
        *title = malloc(strlen(fname) + 32);
        cfail(!*title, "allocate memory", 0);
        sprintf(*title, "iv: %s (%dx%d)", fname, vs.idim[0], vs.idim[1]);
        SDL_SetWindowTitle(window, *title);
    }
}

void showcoords(const SDL_MouseButtonEvent button, const struct ViewState vs) {
    float cc[2];
    int bpos[2] = {button.x, button.y};
    TWICE(cc[j] = ZSH((float)bpos[j] - (float)vs.pan[j] + ZSH(vs.idim[j], vs.zoom - 1.0), -vs.zoom))
    printf("%.0f, %.0f\n", cc[0], cc[1]);
    fflush(stdout);
}

int handlekey(SDL_Keycode sym, struct ViewState* vs, int ci, int fc, const unsigned int wdim[2]) {
    switch (sym) {
        /* bring image back into focus when Space is pressed */
        case SDLK_SPACE:
            TWICE(vs->pan[j] = wdim[j] / 2)
            return 2;
            break;
        /* exit when Esc is pressed */
        case SDLK_ESCAPE:
            return 4;
            break;
        /* navigate image list with arrow keys */
        case SDLK_LEFT:
        case SDLK_UP:
            if (ci > 0) {
                return -1;
            }
            break;
        case SDLK_RIGHT:
        case SDLK_DOWN:
            if (ci < fc - 1) {
                return 1;
            }
            break;
    }
    return 0;
}

void drawbg(SDL_Renderer* ren, const unsigned int wdim[2], const int cw, const int ch, SDL_Texture* act) {
    /* clear to background colour */
    cfail(SDL_RenderClear(ren), "clear screen", 1);
    /* alpha checker background */
    for (int i = 0; i < wdim[0]; i += APS * cw) {
        for (int j = 0; j < wdim[1]; j += APS * ch) {
            cfail(SDL_RenderCopy(ren, act, NULL, &(SDL_Rect){
                .x = i, .y = j, .w = APS * cw, .h = APS * ch
            }), "draw checker background", 1);
        }
    }
}

void drawfg(SDL_Renderer* ren, const struct ViewState vs) {
    int ic[2];
    TWICE(ic[j] = vs.pan[j] - ZSH(vs.idim[j], vs.zoom - 1.0))
    /* render image */
    cfail(SDL_RenderCopy(ren, vs.tex, NULL, &(SDL_Rect){
        .x = ic[0], .y = ic[1],
        .w = ZSH(vs.idim[0], vs.zoom), .h = ZSH(vs.idim[1], vs.zoom)
    }), "display image", 1);
}

int main(int argc, char** argv) {
    /* setup */
    SDL_Init(SDL_INIT_VIDEO);
    atexit(SDL_Quit);
    char* ct = NULL;
    handleargs(argc, argv, &ct);

/* load images before creating window, to determine window size */
    cfail(optind >= argc, "find filename(s) in options", 0);
    int fc = argc - optind;
    SDL_Surface** isurf = loadimages(argv, fc);
    int ci = 0;
    int iw = isurf[ci]->w;
    int ih = isurf[ci]->h;

/* create window and renderer */
    char* title = NULL;
    if (ct) {
        title = ct;
    } else {
        title = malloc(strlen(argv[optind]) + 32);
        cfail(!title, "allocate memory", 0);
        sprintf(title, "iv: %s (%dx%d)", argv[optind], iw, ih);
    }
    SDL_Window* window = SDL_CreateWindow(
        title, SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, iw, ih,
        SDL_WINDOW_RESIZABLE
    );
    cfail(!window, "create window", 1);
    SDL_Renderer* ren = SDL_CreateRenderer(window, -1, 0);
    cfail(!ren, "create renderer", 1);

/* make images into textures */
    int cw = 64, ch = 64;
    SDL_Texture* act = checker(ren, cw, ch);
    struct ViewState* sl = calloc(fc, sizeof(struct ViewState));
    for (int i = 0; i < fc; i++) {
        sl[i].tex = SDL_CreateTextureFromSurface(ren, isurf[i]);
        cfail(!sl[i].tex, "create texture", 1);
        sl[i].idim[0] = isurf[i]->w;
        sl[i].idim[1] = isurf[i]->h;
        TWICE(sl[i].pan[j] = sl[i].idim[j] / 2)
        SDL_FreeSurface(isurf[i]);
    }

/* background (transparent black) */
    cfail(SDL_SetRenderDrawColor(ren, 0, 0, 0, 0), "set colour", 1);

SDL_Event ev;
    /* time measurements for framerate limitation */
    uint32_t ta = SDL_GetTicks();
    uint32_t tb;
    int r = 1;
    /* only bother to redraw if an event that requires it is found */
    int ef;
    /* window size */
    unsigned int wdim[2] = {iw, ih};
    /* mouse position */
    int mpos[2];
    int iic;
    float dz;

while (r) {
        ef = 0;
        while (SDL_PollEvent(&ev)) {
            switch (ev.type) {

case SDL_KEYUP:
                    iic = 0;
                    switch (handlekey(ev.key.keysym.sym, &sl[ci], ci, fc, wdim)) {
                        case 4:
                            r = 0;
                            break;
                        case 2:
                            ef = 1;
                            break;
                        case 1:
                            iic = 1;
                            ci++;
                            break;
                        case -1:
                            iic = 1;
                            ci--;
                            break;
                    }
                    if (iic) {
                        ef = 1;
                        updatetitle(window, ct, &title, argv[optind + ci], sl[ci]);
                    }
                    break;

case SDL_MOUSEBUTTONDOWN:
                    /* output coordinates of cursor in image on middle-click */
                    if (ev.button.button == 2) {
                        showcoords(ev.button, sl[ci]);
                    }
                    /* bring image back into focus on right-click */
                    if (ev.button.button == 3) {
                        TWICE(sl[ci].pan[j] = wdim[j] / 2)
                        ef = 1;
                    }
                    break;

case SDL_MOUSEMOTION:
                    /* pan-dragging if mouse is down */
                    if (SDL_GetMouseState(NULL, NULL) & SDL_BUTTON(1)) {
                        int hid, rhid;
                        int rel[2] = {ev.motion.xrel, ev.motion.yrel};
                        /* clamp panning to edges of window */
                        TWICE(
                            /* scaled (onscreen) image size, halved */
                            hid = ZSH(sl[ci].idim[j], sl[ci].zoom - 1.0);
                            rhid = wdim[j] - hid;
                            if (2 * hid > wdim[j]) {
                                int tmp = hid;
                                hid = rhid;
                                rhid = tmp;
                            }
                            sl[ci].pan[j] = CLAMP(
                                hid, sl[ci].pan[j] + rel[j], rhid
                            );
                        )
                        ef = 1;
                    }
                    mpos[0] = ev.motion.x;
                    mpos[1] = ev.motion.y;
                    break;

case SDL_MOUSEWHEEL:
                    /* scrolling changes zoom */
                    dz = DZDS * ev.wheel.y;
                    sl[ci].zoom += dz;
                    TWICE(sl[ci].pan[j] = mpos[j] - ZSH((mpos[j] - sl[ci].pan[j]), dz))
                    ef = 1;
                    break;

case SDL_QUIT:
                    /* exit upon a quit signal */
                    r = 0;
                    break;

case SDL_WINDOWEVENT:
                    switch (ev.window.event) {
                        /* exit when window is closed */
                        case SDL_WINDOWEVENT_CLOSE:
                            r = 0;
                            break;
                        /* redraw required */
                        case SDL_WINDOWEVENT_EXPOSED:
                            ef = 1;
                            break;
                        case SDL_WINDOWEVENT_SIZE_CHANGED:
                            wdim[0] = ev.window.data1;
                            wdim[1] = ev.window.data2;
                            break;
                    }
                    break;

}
        }

if (ef) {
            drawbg(ren, wdim, cw, ch, act);
            drawfg(ren, sl[ci]);
            SDL_RenderPresent(ren);
        }

/* limit framerate */
        tb = SDL_GetTicks();
        if (tb - ta < FRAMETIME) {
            SDL_Delay(FRAMETIME - (tb - ta));
        }
        ta = tb;
    }

SDL_DestroyWindow(window);
    return 0;
}

iv

Fix panning and pedantries