{render,config}: allow specifying wallpaper anchor position

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: Iee73e9d149e85d2c00eaba4be25d42bd6a6a6964

include/chroma.h

@@ -44,6 +44,19 @@ typedef enum {
   CHROMA_SCALE_CENTER = 3   // center image at original size
 } chroma_scale_mode_t;
 
+// Anchor positions for wallpaper placement
+typedef enum {
+  CHROMA_ANCHOR_CENTER = 0,      // center of the output (default)
+  CHROMA_ANCHOR_TOP = 1,         // top edge, centered horizontally
+  CHROMA_ANCHOR_BOTTOM = 2,      // bottom edge, centered horizontally
+  CHROMA_ANCHOR_LEFT = 3,        // left edge, centered vertically
+  CHROMA_ANCHOR_RIGHT = 4,       // right edge, centered vertically
+  CHROMA_ANCHOR_TOP_LEFT = 5,    // top-left corner
+  CHROMA_ANCHOR_TOP_RIGHT = 6,   // top-right corner
+  CHROMA_ANCHOR_BOTTOM_LEFT = 7, // bottom-left corner
+  CHROMA_ANCHOR_BOTTOM_RIGHT = 8 // bottom-right corner
+} chroma_anchor_t;
+
 // Image filtering quality settings
 typedef enum {
   CHROMA_FILTER_NEAREST = 0,  // nearest neighbor filtering (pixelated)
@@ -90,6 +103,7 @@ typedef struct {
   // Configuration for this output
   chroma_scale_mode_t scale_mode;
   chroma_filter_quality_t filter_quality;
+  chroma_anchor_t anchor;
   bool config_loaded;
 
   // OpenGL resource cache
@@ -108,6 +122,7 @@ typedef struct {
   char image_path[MAX_PATH_LEN];
   chroma_scale_mode_t scale_mode;
   chroma_filter_quality_t filter_quality;
+  chroma_anchor_t anchor;
 } chroma_config_mapping_t;
 
 // Application configuration
@@ -120,6 +135,7 @@ typedef struct {
   // Global scaling and filtering settings (used as defaults)
   chroma_scale_mode_t default_scale_mode;
   chroma_filter_quality_t default_filter_quality;
+  chroma_anchor_t default_anchor;
 
   // Image downsampling settings
   bool enable_downsampling; // enable automatic downsampling
@@ -231,7 +247,8 @@ const char *chroma_config_get_image_for_output(chroma_config_t *config,
                                                const char *output_name);
 int chroma_config_get_mapping_for_output(
     chroma_config_t *config, const char *output_name,
-    chroma_scale_mode_t *scale_mode, chroma_filter_quality_t *filter_quality);
+    chroma_scale_mode_t *scale_mode, chroma_filter_quality_t *filter_quality,
+    chroma_anchor_t *anchor);
 
 void chroma_config_print(const chroma_config_t *config);
 

src/config.c

@@ -6,8 +6,6 @@
 
 #include "../include/chroma.h"
 
-// Default configuration values
-
 static char *trim_whitespace(char *str) {
   char *end;
 
@@ -122,11 +120,71 @@ static const char *filter_quality_to_string(chroma_filter_quality_t quality) {
   }
 }
 
+// Parse anchor position from string
+static chroma_anchor_t parse_anchor(const char *value) {
+  if (!value)
+    return CHROMA_ANCHOR_CENTER;
+
+  if (strcasecmp(value, "center") == 0) {
+    return CHROMA_ANCHOR_CENTER;
+  } else if (strcasecmp(value, "top") == 0) {
+    return CHROMA_ANCHOR_TOP;
+  } else if (strcasecmp(value, "bottom") == 0) {
+    return CHROMA_ANCHOR_BOTTOM;
+  } else if (strcasecmp(value, "left") == 0) {
+    return CHROMA_ANCHOR_LEFT;
+  } else if (strcasecmp(value, "right") == 0) {
+    return CHROMA_ANCHOR_RIGHT;
+  } else if (strcasecmp(value, "top-left") == 0 ||
+             strcasecmp(value, "topleft") == 0) {
+    return CHROMA_ANCHOR_TOP_LEFT;
+  } else if (strcasecmp(value, "top-right") == 0 ||
+             strcasecmp(value, "topright") == 0) {
+    return CHROMA_ANCHOR_TOP_RIGHT;
+  } else if (strcasecmp(value, "bottom-left") == 0 ||
+             strcasecmp(value, "bottomleft") == 0) {
+    return CHROMA_ANCHOR_BOTTOM_LEFT;
+  } else if (strcasecmp(value, "bottom-right") == 0 ||
+             strcasecmp(value, "bottomright") == 0) {
+    return CHROMA_ANCHOR_BOTTOM_RIGHT;
+  }
+
+  chroma_log("WARN", "Unknown anchor: %s (using center)", value);
+  return CHROMA_ANCHOR_CENTER;
+}
+
+// Get string representation of anchor position
+static const char *anchor_to_string(chroma_anchor_t anchor) {
+  switch (anchor) {
+  case CHROMA_ANCHOR_CENTER:
+    return "center";
+  case CHROMA_ANCHOR_TOP:
+    return "top";
+  case CHROMA_ANCHOR_BOTTOM:
+    return "bottom";
+  case CHROMA_ANCHOR_LEFT:
+    return "left";
+  case CHROMA_ANCHOR_RIGHT:
+    return "right";
+  case CHROMA_ANCHOR_TOP_LEFT:
+    return "top-left";
+  case CHROMA_ANCHOR_TOP_RIGHT:
+    return "top-right";
+  case CHROMA_ANCHOR_BOTTOM_LEFT:
+    return "bottom-left";
+  case CHROMA_ANCHOR_BOTTOM_RIGHT:
+    return "bottom-right";
+  default:
+    return "unknown";
+  }
+}
+
 // Output-to-image mapping
 static int add_output_mapping(chroma_config_t *config, const char *output_name,
                               const char *image_path,
                               chroma_scale_mode_t scale_mode,
-                              chroma_filter_quality_t filter_quality) {
+                              chroma_filter_quality_t filter_quality,
+                              chroma_anchor_t anchor) {
   if (!config || !output_name || !image_path) {
     return CHROMA_ERROR_INIT;
   }
@@ -159,12 +217,14 @@ static int add_output_mapping(chroma_config_t *config, const char *output_name,
   strcpy(mapping->image_path, image_path);
   mapping->scale_mode = scale_mode;
   mapping->filter_quality = filter_quality;
+  mapping->anchor = anchor;
 
   config->mapping_count++;
 
-  chroma_log("DEBUG", "Added mapping: %s -> %s (scale: %s, filter: %s)",
+  chroma_log(
-             output_name, image_path, scale_mode_to_string(scale_mode),
+      "DEBUG", "Added mapping: %s -> %s (scale: %s, filter: %s, anchor: %s)",
-             filter_quality_to_string(filter_quality));
+      output_name, image_path, scale_mode_to_string(scale_mode),
+      filter_quality_to_string(filter_quality), anchor_to_string(anchor));
   chroma_log("TRACE", "Output mapping %d: '%s' -> '%s' (path length: %zu)",
              config->mapping_count, output_name, image_path, path_len);
   return CHROMA_OK;
@@ -183,6 +243,7 @@ static void init_default_config(chroma_config_t *config) {
   // Set default scaling and filtering
   config->default_scale_mode = CHROMA_SCALE_FILL;
   config->default_filter_quality = CHROMA_FILTER_LINEAR;
+  config->default_anchor = CHROMA_ANCHOR_CENTER;
 
   // Set default downsampling settings
   config->enable_downsampling = true; // enable by default, performance etc.
@@ -286,6 +347,10 @@ static int parse_config_line(chroma_config_t *config, char *line,
     config->enable_downsampling = parse_bool(value);
     chroma_log("DEBUG", "Set downsampling: %s",
                config->enable_downsampling ? "enabled" : "disabled");
+  } else if (strcasecmp(key, "anchor") == 0) {
+    config->default_anchor = parse_anchor(value);
+    chroma_log("DEBUG", "Set default anchor: %s",
+               anchor_to_string(config->default_anchor));
   } else if (strcasecmp(key, "max_output_width") == 0) {
     int width = atoi(value);
     if (width > 0 && width <= 16384) { // Reasonable limits
@@ -351,6 +416,10 @@ static int parse_config_line(chroma_config_t *config, char *line,
         mapping->filter_quality = parse_filter_quality(value);
         chroma_log("DEBUG", "Set filter quality for output %s: %s", output_name,
                    filter_quality_to_string(mapping->filter_quality));
+      } else if (strcasecmp(property, "anchor") == 0) {
+        mapping->anchor = parse_anchor(value);
+        chroma_log("DEBUG", "Set anchor for output %s: %s", output_name,
+                   anchor_to_string(mapping->anchor));
       } else {
         chroma_log("WARN", "Unknown output property: %s (line %d)", property,
                    line_number);
@@ -375,7 +444,8 @@ static int parse_config_line(chroma_config_t *config, char *line,
 
     if (add_output_mapping(config, output_name, path_to_validate,
                            config->default_scale_mode,
-                           config->default_filter_quality) != CHROMA_OK) {
+                           config->default_filter_quality,
+                           config->default_anchor) != CHROMA_OK) {
       chroma_log("ERROR", "Failed to add output mapping: %s -> %s", output_name,
                  path_to_validate);
       if (expanded_path) {
@@ -518,12 +588,13 @@ const char *chroma_config_get_image_for_output(chroma_config_t *config,
   return NULL;
 }
 
-// Get configuration mapping for output, including scale mode and filter
+// Get configuration mapping for output, including scale mode, filter
-// quality
+// quality, and anchor
 int chroma_config_get_mapping_for_output(
     chroma_config_t *config, const char *output_name,
-    chroma_scale_mode_t *scale_mode, chroma_filter_quality_t *filter_quality) {
+    chroma_scale_mode_t *scale_mode, chroma_filter_quality_t *filter_quality,
-  if (!config || !output_name || !scale_mode || !filter_quality) {
+    chroma_anchor_t *anchor) {
+  if (!config || !output_name || !scale_mode || !filter_quality || !anchor) {
     return CHROMA_ERROR_INIT;
   }
 
@@ -532,10 +603,13 @@ int chroma_config_get_mapping_for_output(
     if (strcmp(config->mappings[i].output_name, output_name) == 0) {
       *scale_mode = config->mappings[i].scale_mode;
       *filter_quality = config->mappings[i].filter_quality;
+      *anchor = config->mappings[i].anchor;
       chroma_log("DEBUG",
-                 "Found specific mapping for output %s: scale=%s, filter=%s",
+                 "Found specific mapping for output %s: scale=%s, filter=%s, "
+                 "anchor=%s",
                  output_name, scale_mode_to_string(*scale_mode),
-                 filter_quality_to_string(*filter_quality));
+                 filter_quality_to_string(*filter_quality),
+                 anchor_to_string(*anchor));
       return CHROMA_OK;
     }
   }
@@ -543,14 +617,14 @@ int chroma_config_get_mapping_for_output(
   // Return defaults if no specific mapping found
   *scale_mode = config->default_scale_mode;
   *filter_quality = config->default_filter_quality;
-  chroma_log("DEBUG", "Using defaults for output %s: scale=%s, filter=%s",
+  *anchor = config->default_anchor;
-             output_name, scale_mode_to_string(*scale_mode),
+  chroma_log(
-             filter_quality_to_string(*filter_quality));
+      "DEBUG", "Using defaults for output %s: scale=%s, filter=%s, anchor=%s",
+      output_name, scale_mode_to_string(*scale_mode),
+      filter_quality_to_string(*filter_quality), anchor_to_string(*anchor));
   return CHROMA_OK;
 }
 
-
-
 // Print current configuration for debugging
 void chroma_config_print(const chroma_config_t *config) {
   if (!config) {

src/core.c

@@ -112,19 +112,21 @@ static int assign_wallpaper_to_output(chroma_state_t *state,
   // Store old configuration values for comparison
   chroma_scale_mode_t old_scale_mode = output->scale_mode;
   chroma_filter_quality_t old_filter_quality = output->filter_quality;
+  chroma_anchor_t old_anchor = output->anchor;
   bool had_config = output->config_loaded;
 
-  // Load configuration for this output (scale mode and filter quality)
+  // Load configuration for this output (scale mode, filter quality, anchor)
   if (chroma_config_get_mapping_for_output(
           &state->config, output->name ? output->name : "unknown",
-          &output->scale_mode, &output->filter_quality) == CHROMA_OK) {
+          &output->scale_mode, &output->filter_quality, &output->anchor) == CHROMA_OK) {
     output->config_loaded = true;
-    chroma_log("DEBUG", "Loaded config for output %u: scale=%d, filter=%d",
+    chroma_log("DEBUG", "Loaded config for output %u: scale=%d, filter=%d, anchor=%d",
-               output->id, output->scale_mode, output->filter_quality);
+               output->id, output->scale_mode, output->filter_quality, output->anchor);
 
     // Check if configuration changed and invalidate texture if needed
     if (had_config && (old_scale_mode != output->scale_mode ||
-                       old_filter_quality != output->filter_quality)) {
+                       old_filter_quality != output->filter_quality ||
+                       old_anchor != output->anchor)) {
       chroma_output_invalidate_texture(output);
       output->vbo_dirty = true; // VBO needs update for new scale mode
       chroma_log("DEBUG",

src/render.c

@@ -41,8 +41,9 @@ static void get_gl_filter_params(chroma_filter_quality_t quality,
   }
 }
 
-// Calculate texture coordinates based on scaling mode
+// Calculate texture coordinates based on scaling mode and anchor position
 static void calculate_texture_coords(chroma_scale_mode_t scale_mode,
+                                     chroma_anchor_t anchor,
                                      int image_width, int image_height,
                                      int output_width, int output_height,
                                      float tex_coords[8]) {
@@ -142,6 +143,72 @@ static void calculate_texture_coords(chroma_scale_mode_t scale_mode,
     break;
   }
 
+  // Apply anchor-based offset by shifting the visible crop region
+  // For fill: shift which part of image is shown
+  // For fit/center: shift where the image is positioned
+  // 
+  // Positive shift reveals left/bottom portion
+  // Negative shift reveals right/top portion
+  float u_shift = 0.0f;
+  float v_shift = 0.0f;
+
+  switch (anchor) {
+  case CHROMA_ANCHOR_CENTER:
+    u_shift = 0.0f;
+    v_shift = 0.0f;
+    break;
+  case CHROMA_ANCHOR_TOP:
+    u_shift = 0.0f;
+    v_shift = -0.5f; // shift up to show top of image
+    break;
+  case CHROMA_ANCHOR_BOTTOM:
+    u_shift = 0.0f;
+    v_shift = 0.5f; // shift down to show bottom of image
+    break;
+  case CHROMA_ANCHOR_LEFT:
+    u_shift = -0.5f; // shift left to show left of image
+    v_shift = 0.0f;
+    break;
+  case CHROMA_ANCHOR_RIGHT:
+    u_shift = 0.5f; // shift right to show right of image
+    v_shift = 0.0f;
+    break;
+  case CHROMA_ANCHOR_TOP_LEFT:
+    u_shift = -0.5f;
+    v_shift = -0.5f;
+    break;
+  case CHROMA_ANCHOR_TOP_RIGHT:
+    u_shift = 0.5f;
+    v_shift = -0.5f;
+    break;
+  case CHROMA_ANCHOR_BOTTOM_LEFT:
+    u_shift = -0.5f;
+    v_shift = 0.5f;
+    break;
+  case CHROMA_ANCHOR_BOTTOM_RIGHT:
+    u_shift = 0.5f;
+    v_shift = 0.5f;
+    break;
+  }
+
+  // Calculate the shift amount based on crop/border space available
+  float u_crop = 1.0f - (u2 - u1);
+  float v_crop = 1.0f - (v2 - v1);
+  u1 += u_shift * u_crop;
+  u2 += u_shift * u_crop;
+  v1 += v_shift * v_crop;
+  v2 += v_shift * v_crop;
+
+  // Clamp to valid range [0, 1]
+  if (u1 < 0.0f)
+    u1 = 0.0f;
+  if (u2 > 1.0f)
+    u2 = 1.0f;
+  if (v1 < 0.0f)
+    v1 = 0.0f;
+  if (v2 > 1.0f)
+    v2 = 1.0f;
+
   // Set texture coordinates for quad (bottom-left, bottom-right, top-right,
   // top-left)
   tex_coords[0] = u1;
@@ -688,11 +755,11 @@ int chroma_render_wallpaper(chroma_state_t *state, chroma_output_t *output) {
   // Update VBO only if needed. E.g, image changed, scale mode changed, or first
   // render
   if (output->vbo_dirty) {
-    // Calculate texture coordinates based on scaling mode
+    // Calculate texture coordinates based on scaling mode and anchor
     float tex_coords[8];
-    calculate_texture_coords(output->scale_mode, output->image->width,
+    calculate_texture_coords(output->scale_mode, output->anchor,
-                             output->image->height, output->width,
+                             output->image->width, output->image->height,
-                             output->height, tex_coords);
+                             output->width, output->height, tex_coords);
 
     // Create dynamic vertex data with calculated texture coordinates
     float dynamic_vertices[] = {