vo_opengl: use RPN expressions for user hook sizes

This replaces the previous TRANSFORM by WIDTH, HEIGHT and OFFSET where
WIDTH and HEIGHT are RPN expressions. This allows for more fine-grained
control over the output size, and also makes sure that overwriting
existing textures works more cleanly.

(Also add some more useful bstr functions)

1 files changed, 77 insertions, 7 deletions

diff --git a/video/out/opengl/user_shaders.c b/video/out/opengl/user_shaders.c
index 0c1b765400..0cf80af115 100644
--- a/video/out/opengl/user_shaders.c
+++ b/video/out/opengl/user_shaders.c
@@ -16,6 +16,54 @@
  */
 
 #include "user_shaders.h"
+#include "ctype.h"
+
+static bool parse_rpn_szexpr(struct bstr line, struct szexp out[MAX_SZEXP_SIZE])
+{
+    int pos = 0;
+
+    while (line.len > 0) {
+        struct bstr word = bstr_strip(bstr_splitchar(line, &line, ' '));
+        if (word.len == 0)
+            continue;
+
+        if (pos >= MAX_SZEXP_SIZE)
+            return false;
+
+        struct szexp *exp = &out[pos++];
+
+        if (bstr_eatend0(&word, ".w") || bstr_eatend0(&word, ".width")) {
+            exp->tag = SZEXP_VAR_W;
+            exp->val.varname = word;
+            continue;
+        }
+
+        if (bstr_eatend0(&word, ".h") || bstr_eatend0(&word, ".height")) {
+            exp->tag = SZEXP_VAR_H;
+            exp->val.varname = word;
+            continue;
+        }
+
+        switch (word.start[0]) {
+        case '+': exp->tag = SZEXP_OP2; exp->val.op = SZEXP_OP_ADD; continue;
+        case '-': exp->tag = SZEXP_OP2; exp->val.op = SZEXP_OP_SUB; continue;
+        case '*': exp->tag = SZEXP_OP2; exp->val.op = SZEXP_OP_MUL; continue;
+        case '/': exp->tag = SZEXP_OP2; exp->val.op = SZEXP_OP_DIV; continue;
+        }
+
+        if (isdigit(word.start[0])) {
+            exp->tag = SZEXP_CONST;
+            if (bstr_sscanf(word, "%f", &exp->val.cval) != 1)
+                return false;
+            continue;
+        }
+
+        // Some sort of illegal expression
+        return false;
+    }
+
+    return true;
+}
 
 // Returns false if no more shaders could be parsed
 bool parse_user_shader_pass(struct mp_log *log, struct bstr *body,
@@ -24,14 +72,19 @@ bool parse_user_shader_pass(struct mp_log *log, struct bstr *body,
     if (!body || !out || !body->start || body->len == 0)
         return false;
 
-    *out = (struct gl_user_shader){ .transform = identity_trans };
+    *out = (struct gl_user_shader){
+        .offset = identity_trans,
+        .width = {{ SZEXP_VAR_W, { .varname = bstr0("HOOKED") }}},
+        .height = {{ SZEXP_VAR_H, { .varname = bstr0("HOOKED") }}},
+    };
+
     int hook_idx = 0;
     int bind_idx = 0;
 
     // First parse all the headers
     while (true) {
         struct bstr rest;
-        struct bstr line = bstr_getline(*body, &rest);
+        struct bstr line = bstr_strip(bstr_getline(*body, &rest));
 
         // Check for the presence of the magic line beginning
         if (!bstr_eatstart0(&line, "//!"))
@@ -65,13 +118,30 @@ bool parse_user_shader_pass(struct mp_log *log, struct bstr *body,
             continue;
         }
 
-        if (bstr_eatstart0(&line, "TRANSFORM")) {
-            float sx, sy, ox, oy;
-            if (bstr_sscanf(line, "%f %f %f %f", &sx, &sy, &ox, &oy) != 4) {
-                mp_err(log, "Error while parsing TRANSFORM!\n");
+        if (bstr_eatstart0(&line, "OFFSET")) {
+            float ox, oy;
+            if (bstr_sscanf(line, "%f %f", &ox, &oy) != 2) {
+                mp_err(log, "Error while parsing OFFSET!\n");
+                return false;
+            }
+            out->offset.t[0] = ox;
+            out->offset.t[1] = oy;
+            continue;
+        }
+
+        if (bstr_eatstart0(&line, "WIDTH")) {
+            if (!parse_rpn_szexpr(line, out->width)) {
+                mp_err(log, "Error while parsing WIDTH!\n");
+                return false;
+            }
+            continue;
+        }
+
+        if (bstr_eatstart0(&line, "HEIGHT")) {
+            if (!parse_rpn_szexpr(line, out->height)) {
+                mp_err(log, "Error while parsing HEIGHT!\n");
                 return false;
             }
-            out->transform = (struct gl_transform){{{sx, 0}, {0, sy}}, {ox, oy}};
             continue;
         }