iv

@@ -9,6 +9,7 @@

 #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

@@ -19,13 +20,11 @@

 struct ViewState {

     SDL_Texture* tex;

     /* image dimensions */

-    int iw;

-    int ih;

+    unsigned int idim[2];

     /* zoom level */

     float zoom;

     /* pan position (centre of image) */

-    int px;

-    int py;

+    int pan[2];

 };

 /* if cond is true, exit the program as a failure,

@@ -110,26 +109,24 @@ void updatetitle(SDL_Window* window, const char* ct, char** title, const char* f

         free(*title);

         *title = malloc(strlen(fname) + 32);

         cfail(!*title, "allocate memory", 0);

-        sprintf(*title, "iv: %s (%dx%d)", fname, vs.iw, vs.ih);

+        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) {

-    printf(

-        "%.0f, %.0f\n",

-        ZSH((float)button.x - (float)vs.px + ZSH(vs.iw, vs.zoom - 1.0), -vs.zoom),

-        ZSH((float)button.y - (float)vs.py + ZSH(vs.ih, vs.zoom - 1.0), -vs.zoom)

-    );

+    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, int ww, int wh) {

+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:

-            vs->px = ww / 2;

-            vs->py = wh / 2;

+            TWICE(vs->pan[j] = wdim[j] / 2)

             return 2;

             break;

         /* exit when Esc is pressed */

@@ -153,12 +150,12 @@ int handlekey(SDL_Keycode sym, struct ViewState* vs, int ci, int fc, int ww, int

     return 0;

 }

-void drawbg(SDL_Renderer* ren, const int ww, const int wh, const int cw, const int ch, SDL_Texture* act) {

+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 < ww; i += APS * cw) {

-        for (int j = 0; j < wh; j += APS * ch) {

+    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);

@@ -167,10 +164,12 @@ void drawbg(SDL_Renderer* ren, const int ww, const int wh, const int cw, const i

 }

 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 = vs.px - ZSH(vs.iw, vs.zoom - 1.0), .y = vs.py - ZSH(vs.ih, vs.zoom - 1.0),

-        .w = ZSH(vs.iw, vs.zoom), .h = ZSH(vs.ih, vs.zoom)

+        .x = ic[0], .y = ic[1],

+        .w = ZSH(vs.idim[0], vs.zoom), .h = ZSH(vs.idim[1], vs.zoom)

     }), "display image", 1);

 }

@@ -213,10 +212,9 @@ int main(int argc, char** argv) {

     for (int i = 0; i < fc; i++) {

         sl[i].tex = SDL_CreateTextureFromSurface(ren, isurf[i]);

         cfail(!sl[i].tex, "create texture", 1);

-        sl[i].px = sl[i].iw = isurf[i]->w;

-        sl[i].px /= 2;

-        sl[i].py = sl[i].ih = isurf[i]->h;

-        sl[i].py /= 2;

+        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]);

     }

@@ -231,10 +229,9 @@ int main(int argc, char** argv) {

     /* only bother to redraw if an event that requires it is found */

     int ef;

     /* window size */

-    int ww = iw;

-    int wh = ih;

+    unsigned int wdim[2] = {iw, ih};

     /* mouse position */

-    int mx, my;

+    int mpos[2];

     while (r) {

         ef = 0;

@@ -243,7 +240,7 @@ int main(int argc, char** argv) {

                 case SDL_KEYUP:

                     int iic = 0;

-                    switch (handlekey(ev.key.keysym.sym, &sl[ci], ci, fc, ww, wh)) {

+                    switch (handlekey(ev.key.keysym.sym, &sl[ci], ci, fc, wdim)) {

                         case 4:

                             r = 0;

                             break;

@@ -272,8 +269,7 @@ int main(int argc, char** argv) {

                     }

                     /* bring image back into focus on right-click */

                     if (ev.button.button == 3) {

-                        sl[ci].px = ww / 2;

-                        sl[ci].py = wh / 2;

+                        TWICE(sl[ci].pan[j] = wdim[j] / 2)

                         ef = 1;

                     }

                     break;

@@ -281,32 +277,29 @@ int main(int argc, char** argv) {

                 case SDL_MOUSEMOTION:

                     /* pan-dragging if mouse is down */

                     if (SDL_GetMouseState(NULL, NULL) & SDL_BUTTON(1)) {

-                        int sw = ZSH(sl[ci].iw, sl[ci].zoom - 1.0);

-                        int sh = ZSH(sl[ci].ih, sl[ci].zoom - 1.0);

+                        int hid, big;

+                        int rel[2] = {ev.motion.xrel, ev.motion.yrel};

                         /* clamp panning to edges of window */

-                        int big = 2 * sw > ww;

-                        sl[ci].px = CLAMP(

-                            big ? ww - sw : sw,

-                            sl[ci].px + ev.motion.xrel,

-                            big ? sw : ww - sw

-                        );

-                        big = 2 * sh > wh;

-                        sl[ci].py = CLAMP(

-                            big ? wh - sh : sh,

-                            sl[ci].py + ev.motion.yrel,

-                            big ? sh : wh - sh

-                        );

+                        TWICE(

+                            hid = ZSH(sl[ci].idim[j], sl[ci].zoom - 1.0);

+                            big = 2 * hid > wdim[j];

+                            sl[ci].pan[j] = CLAMP(

+                                big ? wdim[j] - hid : hid,

+                                sl[ci].pan[j] + rel[j],

+                                big ? hid : wdim[j] - hid

+                            )

+                        )

                         ef = 1;

                     }

-                    mx = ev.motion.x;

-                    my = ev.motion.y;

+                    mpos[0] = ev.motion.x;

+                    mpos[1] = ev.motion.y;

                     break;

                 case SDL_MOUSEWHEEL:

                     /* scrolling changes zoom */

-                    sl[ci].zoom += DZDS * ev.wheel.y;

-                    sl[ci].px = mx - ZSH((mx - sl[ci].px), DZDS * ev.wheel.y);

-                    sl[ci].py = my - ZSH((my - sl[ci].py), DZDS * ev.wheel.y);

+                    float 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;

@@ -326,8 +319,8 @@ int main(int argc, char** argv) {

                             ef = 1;

                             break;

                         case SDL_WINDOWEVENT_SIZE_CHANGED:

-                            ww = ev.window.data1;

-                            wh = ev.window.data2;

+                            wdim[0] = ev.window.data1;

+                            wdim[1] = ev.window.data2;

                             break;

                     }

                     break;

@@ -336,7 +329,7 @@ int main(int argc, char** argv) {

         }

         if (ef) {

-            drawbg(ren, ww, wh, cw, ch, act);

+            drawbg(ren, wdim, cw, ch, act);

             drawfg(ren, sl[ci]);

             SDL_RenderPresent(ren);

         }