[async] message queue abstractions

src/backend.h

@@ -16,20 +16,8 @@ int ax__backend_new(
     struct ax_backend** out_bac,
     const char** out_err);
 
-enum {
-    ax_msg_shutdown_TAG,
-    ax_msg_load_font_TAG,
-};
-
-struct ax_msg_shutdown {};
-
-struct ax_msg_load_font {
-    struct ax_theme* theme;
-    int category;
-};
-
 struct msgq* ax__backend_msgq(struct ax_backend*);
+bool ax__backend_is_shutdown(struct ax_backend*);
 
 void ax__backend_wait_for_event(struct ax_backend*);
-
-void ax__backend_step(struct ax_backend*, bool* out_shutdown);
+void ax__backend_step(struct ax_backend*);

src/backend/sdl.c

@@ -1,7 +1,8 @@
 #include "../backend.h"
+#include "../ctxt/theme.h"
 #include "../util/region.h"
 #include "../concurrent/msgq.h"
-#include "../ctxt/theme.h"
+#include "../concurrent/msg.h"
 #include <SDL2/SDL.h>
 #include <SDL2/SDL_ttf.h>
 
@@ -66,37 +67,39 @@ struct msgq* ax__backend_msgq(struct ax_backend* bac)
     return bac->mq;
 }
 
+bool ax__backend_is_shutdown(struct ax_backend* bac)
+{
+    return bac->shutdown;
+}
+
 void ax__backend_wait_for_event(struct ax_backend* bac)
 {
     (void) bac;
 }
 
-void ax__backend_step(struct ax_backend* bac, bool* out_shutdown)
+void ax__backend_step(struct ax_backend* bac)
 {
-    int type;
-    void* data;
     msgq_begin_recv(bac->mq);
-    while ((data = msgq_recv1(bac->mq, &type)) != NULL) {
-        switch (type) {
 
-        case ax_msg_shutdown_TAG:
-            bac->shutdown = true;
-            break;
+    MSGQ_RECV_ALL(bac->mq) {
 
-        case ax_msg_load_font_TAG: {
-            struct ax_msg_load_font* m = data;
-            printf("TODO: load font `%s' (size %zu)\n",
-                   m->theme->font_path[m->category],
-                   m->theme->font_size[m->category]);
-            break;
-        }
+        ON(ax_msg_shutdown,
+           {
+               (void) m;
+               bac->shutdown = true;
+               break;
+           });
+
+        ON(ax_msg_load_font,
+           {
+               printf("TODO: load font `%s' (size %zu)\n",
+                      m->theme->font_path[m->category],
+                      m->theme->font_size[m->category]);
+               break;
+           });
 
         default: break;
-        }
     }
-    msgq_end_recv(bac->mq);
 
-    if (out_shutdown != NULL) {
-        *out_shutdown = bac->shutdown;
-    }
+    msgq_end_recv(bac->mq);
 }

src/concurrent/msg.h

@@ -0,0 +1,14 @@
+#pragma once
+
+enum {
+    ax_msg_shutdown_TAG,
+    ax_msg_load_font_TAG,
+};
+
+struct ax_msg_shutdown {
+};
+
+struct ax_msg_load_font {
+    struct ax_theme* theme;
+    int category;
+};

src/concurrent/msgq.h

@@ -21,9 +21,22 @@ struct msgq* msgq_new(struct rgn* init_rgn);
 void* msgq_begin_send(struct msgq* mq, int type, size_t payload_size);
 void msgq_end_send(struct msgq* mq);
 
-#define msgq_begin_send_typed(_mq, _ty)                                  \
-    ((struct _ty*) msgq_begin_send(_mq, _ty ## _TAG, sizeof(struct _ty)))
-
 void msgq_begin_recv(struct msgq* mq);
 void* msgq_recv1(struct msgq* mq, int* out_type);
 void msgq_end_recv(struct msgq* mq);
+
+// helper macros
+
+#define msgq_begin_send_typed(_mq, ty)                                  \
+    ((struct ty*) msgq_begin_send(_mq, ty ## _TAG, sizeof(struct ty)))
+
+#define MSGQ_RECV_ALL(_mq)                                      \
+    int mqr__type; void* mqr__data;                             \
+    while ((mqr__data = msgq_recv1(_mq, &mqr__type)) != NULL)   \
+        switch (mqr__type)
+
+#define ON(ty, _body)                           \
+    case ty ## _TAG: {                          \
+        const struct ty* m = mqr__data;         \
+        _body;                                  \
+    }

src/ctxt/theme.c

@@ -3,6 +3,7 @@
 #include "../util/region.h"
 #include "../backend.h"
 #include "../concurrent/msgq.h"
+#include "../concurrent/msg.h"
 #include <inttypes.h>
 
 static const char* default_font_path(struct rgn* rgn)

test/main.c

@@ -22,9 +22,8 @@ int main(void)
 
     ax_log(ax, "Got here\n");
 
-    bool shutdown = false;
     ax__backend_wait_for_event(ax->bac);
-    ax__backend_step(ax->bac, &shutdown);
+    ax__backend_step(ax->bac);
 
 //cleanup:
     if (rv != 0) {