Skip the table for an empty init sequence; test it

Identical lambdas can carry separate static state, so callers need a way
to keep such tables apart while still getting a collision free name.

esphome/codegen.py

@@ -40,6 +40,7 @@ from esphome.cpp_generator import (  # noqa: F401
     progmem_array,
     safe_exp,
     set_cpp_standard,
+    shared_progmem_array,
     statement,
     static_const_array,
     static_function,

esphome/components/st7701s/display.py

@@ -181,7 +181,9 @@ async def to_code(config: ConfigType) -> None:
     sequence = []
     for seq in config[CONF_INIT_SEQUENCE]:
         sequence.extend(seq)
-    cg.add(var.set_init_sequence(sequence))
+    if sequence:
+        table = cg.shared_progmem_array("st7701s_init_sequence", cg.uint8, sequence)
+        cg.add(var.set_init_sequence(table, len(sequence)))
     cg.add(var.set_color_mode(COLOR_ORDERS[config[CONF_COLOR_ORDER]]))
     cg.add(var.set_invert_colors(config[CONF_INVERT_COLORS]))
     cg.add(var.set_hsync_pulse_width(config[CONF_HSYNC_PULSE_WIDTH]))

esphome/components/st7701s/st7701s.cpp

@@ -144,14 +144,14 @@ void ST7701S::write_sequence_(uint8_t cmd, size_t len, const uint8_t *bytes) {
 }
 
 void ST7701S::write_init_sequence_() {
-  for (size_t i = 0; i != this->init_sequence_.size();) {
+  for (size_t i = 0; i != this->init_sequence_len_;) {
     uint8_t cmd = this->init_sequence_[i++];
     size_t len = this->init_sequence_[i++];
     if (len == ST7701S_DELAY_FLAG) {
       ESP_LOGV(TAG, "Delay %dms", cmd);
       delay(cmd);
     } else {
-      this->write_sequence_(cmd, len, &this->init_sequence_[i]);
+      this->write_sequence_(cmd, len, this->init_sequence_ + i);
       i += len;
       ESP_LOGV(TAG, "Command %X, %d bytes", cmd, len);
       if (cmd == SW_RESET_CMD)

esphome/components/st7701s/st7701s.h

@@ -62,7 +62,10 @@ class ST7701S final : public display::Display,
   void set_vsync_pulse_width(uint16_t vsync_pulse_width) { this->vsync_pulse_width_ = vsync_pulse_width; }
   void set_vsync_back_porch(uint16_t vsync_back_porch) { this->vsync_back_porch_ = vsync_back_porch; }
   void set_vsync_front_porch(uint16_t vsync_front_porch) { this->vsync_front_porch_ = vsync_front_porch; }
-  void set_init_sequence(const std::vector<uint8_t> &init_sequence) { this->init_sequence_ = init_sequence; }
+  void set_init_sequence(const uint8_t *init_sequence, size_t len) {
+    this->init_sequence_ = init_sequence;
+    this->init_sequence_len_ = len;
+  }
   void set_mirror_x(bool mirror_x) { this->mirror_x_ = mirror_x; }
   void set_mirror_y(bool mirror_y) { this->mirror_y_ = mirror_y; }
   void set_offsets(int16_t offset_x, int16_t offset_y) {
@@ -95,7 +98,9 @@ class ST7701S final : public display::Display,
   uint16_t vsync_pulse_width_ = 10;
   uint16_t vsync_back_porch_ = 10;
   uint16_t vsync_front_porch_ = 10;
-  std::vector<uint8_t> init_sequence_;
+  // Shared PROGMEM table
+  const uint8_t *init_sequence_{nullptr};
+  size_t init_sequence_len_{0};
   uint32_t pclk_frequency_ = 16 * 1000 * 1000;
   bool pclk_inverted_{true};
 

esphome/cpp_generator.py

@@ -19,7 +19,12 @@ from esphome.core import (
     TimePeriodNanoseconds,
     TimePeriodSeconds,
 )
-from esphome.helpers import cpp_string_escape, indent, indent_all_but_first_and_last
+from esphome.helpers import (
+    cpp_string_escape,
+    ensure_unique_string,
+    indent,
+    indent_all_but_first_and_last,
+)
 from esphome.types import Expression, SafeExpType, TemplateArgsType
 from esphome.util import OrderedDict
 from esphome.yaml_util import ESPHomeDataBase
@@ -463,6 +468,36 @@ def progmem_array(id_, rhs) -> "MockObj":
     return obj
 
 
+def shared_progmem_array(
+    name: str, type_: "MockObjClass", rhs: SafeExpType, *, share: bool = True
+) -> "MockObj":
+    """Emit a global PROGMEM array once per distinct type and contents; later calls reuse it.
+
+    The array is ``static constexpr``, so elements must be constant expressions and lambdas
+    must be captureless. Its name is made unique against every config id and variable.
+    ``share=False`` always emits a new array, e.g. for lambdas that may keep static state.
+    """
+    from esphome.config import iter_ids
+    from esphome.config_validation import RESERVED_IDS
+
+    arrays: dict[str, MockObj] = CORE.data.setdefault("shared_progmem_array", {})
+    rhs = safe_exp(rhs)
+    key = f"{type_} {rhs}"
+    if share and (array := arrays.get(key)) is not None:
+        return array
+    used = {str(i) for i, _ in iter_ids(CORE.config)}
+    used |= {str(i) for i in CORE.variables}
+    used |= set(RESERVED_IDS) | CORE.loaded_integrations
+    id_ = ID(ensure_unique_string(name, used), is_declaration=True, type=type_)
+    # Global, so any scope can use it; anything a lambda references is already declared.
+    CORE.add_global(ProgmemAssignmentExpression(type_, id_, rhs))
+    array = MockObj(id_, ".")
+    CORE.register_variable(id_, array)
+    if share:
+        arrays[key] = array
+    return array
+
+
 def static_const_array(id_, rhs) -> "MockObj":
     rhs = safe_exp(rhs)
     obj = MockObj(id_, ".")

tests/component_tests/st7701s/test_init_sequence.py

@@ -0,0 +1,68 @@
+"""Tests for the st7701s init sequence codegen."""
+
+from collections.abc import Callable
+from pathlib import Path
+import re
+
+_YAML = """
+esphome:
+  name: st7701s-test
+esp32:
+  board: esp32-s3-devkitc-1
+  framework:
+    type: esp-idf
+psram:
+  mode: octal
+spi:
+  clk_pin: 10
+  mosi_pin: 11
+display:
+  - platform: st7701s
+    id: panel
+    dimensions:
+      width: 480
+      height: 480
+    cs_pin: 44
+    de_pin: 18
+    hsync_pin: 16
+    vsync_pin: 17
+    pclk_pin: 21
+    init_sequence: {init_sequence}
+    data_pins: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 13, 14, 15, 38, 39]
+"""
+
+
+def test_init_sequence_is_progmem_table(
+    generate_main: Callable[[str | Path], str],
+    tmp_path: Path,
+) -> None:
+    """The init sequence is a PROGMEM table instead of a vector copied at boot."""
+    yaml_file = tmp_path / "st7701s.yaml"
+    yaml_file.write_text(
+        _YAML.format(init_sequence="[1, [0x23, 0xA, 0xB], delay 20ms]")
+    )
+
+    main_cpp = generate_main(yaml_file)
+
+    call = re.search(r"panel->set_init_sequence\((\w+), (\d+)\);", main_cpp)
+    assert call is not None
+    table = re.search(
+        rf"static constexpr uint8_t {call.group(1)}\[\] PROGMEM = \{{([^;]*)\}};",
+        main_cpp,
+    )
+    assert table is not None
+    assert len(table.group(1).split(",")) == int(call.group(2))
+
+
+def test_empty_init_sequence_emits_no_table(
+    generate_main: Callable[[str | Path], str],
+    tmp_path: Path,
+) -> None:
+    """An empty init sequence leaves the display without a table instead of a zero length array."""
+    yaml_file = tmp_path / "st7701s.yaml"
+    yaml_file.write_text(_YAML.format(init_sequence="[]"))
+
+    main_cpp = generate_main(yaml_file)
+
+    assert "st7701s_init_sequence" not in main_cpp
+    assert "set_init_sequence" not in main_cpp

tests/unit_tests/test_cpp_generator.py

@@ -4,6 +4,7 @@ import math
 import pytest
 
 from esphome import cpp_generator as cg, cpp_types as ct
+from esphome.core import CORE, ID
 
 
 class TestExpressions:
@@ -808,3 +809,39 @@ async def test_templatable__lambda_with_std_string() -> None:
     result = await cg.templatable(lambda_obj, [], ct.std_string)
 
     assert isinstance(result, cg.LambdaExpression)
+
+
+class TestSharedProgmemArray:
+    def test_identical_contents_share_one_array(self) -> None:
+        CORE.config = {}
+        a = cg.shared_progmem_array("table", ct.uint8, [1, 2, 3])
+        b = cg.shared_progmem_array("table", ct.uint8, [1, 2, 3])
+        c = cg.shared_progmem_array("table", ct.uint8, [4])
+        assert a is b
+        assert str(a) != str(c)
+        assert sum("PROGMEM" in str(st) for st in CORE.global_statements) == 2
+        assert not any("PROGMEM" in str(st) for st in CORE.main_statements)
+
+    def test_share_false_always_emits_a_new_array(self) -> None:
+        CORE.config = {}
+        a = cg.shared_progmem_array("table", ct.uint8, [1], share=False)
+        b = cg.shared_progmem_array("table", ct.uint8, [1], share=False)
+        assert str(a) != str(b)
+        assert sum("PROGMEM" in str(st) for st in CORE.global_statements) == 2
+
+    def test_same_contents_different_type_are_separate(self) -> None:
+        CORE.config = {}
+        a = cg.shared_progmem_array("table", ct.uint8, [1])
+        b = cg.shared_progmem_array("table", ct.uint16, [1])
+        assert str(a) != str(b)
+
+    def test_name_avoids_config_ids(self) -> None:
+        CORE.config = {"sensor": [{"id": ID("table", is_declaration=True)}]}
+        array = cg.shared_progmem_array("table", ct.uint8, [1])
+        assert str(array) == "table_2"
+
+    def test_name_avoids_registered_variables(self) -> None:
+        CORE.config = {}
+        CORE.register_variable(ID("table", is_declaration=True), cg.MockObj("table"))
+        array = cg.shared_progmem_array("table", ct.uint8, [1])
+        assert str(array) == "table_2"