Crouching/sneaking with shift, move slower and not fall of ledges

[satoshinm]

Allow moving more carefully when holding down the "shift key", aka crouching or sneaking. Slows down movement and prevents falling off an edge of the blocks. Important for survival.

[satoshinm]

Gravity is implemented in handle_movement(), if not flying then dy each time step, and drop down unless colliding vertically with a block:

        if (g->flying) {
            dy = 0;
        }
        else {
            dy -= ut * 25;
            dy = MAX(dy, -250);
        }
         s->x += vx;
         s->y += vy + dy * ut;
         s->z += vz;
         if (collide(2, &s->x, &s->y, &s->z)) {
             dy = 0;

collide() clamps its input coordinates on output to right up to a block. Returns 1 if y collided, else 0. If returns 0, then the player is falling. This is where crouching could be implemented, canceling the x/z movement:

             dy = 0;
+        } else {
+            if (crouching && !g->flying) {
+                s->y -= vy + dy * ut; // don't fall off ledges
+                // TODO: allow sliding along edges in one axis
+                s->x -= vx;
+                s->z -= vz;

but this doesn't let the player "slide" along the edges while not falling off. Ideally want to allow movement in the direction that wouldn't cause the player to fall off. They should be able to slide in either direction, as long as it doesn't fall (no flying). Stuck on this, my half-baked solutions either allow floating or no sliding:

--- a/src/main.c
+++ b/src/main.c
@@ -2942,9 +2942,9 @@ void handle_movement(double dt) {
     }
     float vx, vy = 0, vz;
     get_motion_vector(g->flying, sz, sx, s->rx, s->ry, &vx, &vy, &vz);
+    int jumping = glfwGetKey(g->window, CRAFT_KEY_JUMP) || touch_jump;
+    int crouching = glfwGetKey(g->window, CRAFT_KEY_CROUCH);
     if (!g->typing) {
-        int jumping = glfwGetKey(g->window, CRAFT_KEY_JUMP) || touch_jump;
-        int crouching = glfwGetKey(g->window, CRAFT_KEY_CROUCH);
 
         if (g->gamepad_connected != -1) {
             if (g->gamepad_state.digitalButton[GAMEPAD_A]) jumping = 1;
@@ -2986,6 +2986,7 @@ void handle_movement(double dt) {
     vx = vx * ut * speed;
     vy = vy * ut * speed;
     vz = vz * ut * speed;
+
     for (int i = 0; i < step; i++) {
         if (g->flying) {
             dy = 0;
@@ -2994,11 +2995,27 @@ void handle_movement(double dt) {
             dy -= ut * 25;
             dy = MAX(dy, -250);
         }
-        s->x += vx;
-        s->y += vy + dy * ut;
-        s->z += vz;
-        if (collide(2, &s->x, &s->y, &s->z)) {
+        float tx = s->x + vx;
+        float ty = s->y + vy + dy * ut;
+        float tz = s->z + vz;
+
+        if (collide(2, &tx, &ty, &tz)) {
             dy = 0;
+            s->x = tx;
+            s->y = ty;
+            s->z = tz;
+        } else {
+            // would fall
+            if (crouching && !g->flying) {
+                if (sx != 0) s->x = tx;
+                //s->y = ty;
+                if (sz != 0) s->z = tz;
+                printf("x %f, y %f, z %f\n", s->x-tx, s->y-ty, s->z-tz);
+            } else {
+                s->x = tx;
+                s->y = ty;
+                s->z = tz;
+            }
         }
     }
     if (s->y < 0) {

[satoshinm]

Introduces more problems than it solves, so reverted this feature (but kept the small refactoring changes surrounding it). When fixing again, make sure to avoid #181 crouching allows hovering in midair while falling and #180 crouching doesn't allow sliding along edges. Maybe there is some simpler implementation to avoid these problems I am missing.